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  • Boost.Python wrapping hierarchies avoiding diamond inheritance

    - by stbuton
    I'm having some trouble seeing what the best way to wrap a series of classes with Boost.Python while avoiding messy inheritance problems. Say I have the classes A, B, and C with the following structure: struct A { virtual void foo(); virtual void bar(); virtual void baz(); }; struct B : public A { virtual void quux(); }; struct C : public A { virtual void foobar(); }; I want to wrap all classes A, B, and C such that they are extendable from Python. The normal method for accomplishing this would be along the lines of: struct A_Wrapper : public A, boost::python::wrapper<A> { //dispatch logic for virtual functions }; Now for classes B and C which extend from A I would like to be able to inherit and share the wrapping implementation for A. So I'd like to be able to do something along the lines of: struct B_Wrapper : public B, public A_Wrapper, public boost::python::wrapper<B> { //dispatch logic specific for B }; struct C_Wrapper : public C, public A_Wrapper, public boost::python::wrapper<C> { //dispatch logic specific for C } However, it seems like that would introduce all manner of nastiness with the double inheritance of the boost wrapper base and the double inheritance of A in the B_Wrapper and C_Wrapper objects. Is there a common way that this instance is solved that I'm missing? thanks.

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  • Java or Python for internet application?

    - by jpartogi
    In choosing a technology for internet applications where the number of users may scale over time, which one should we consider: Java or Python? What are the considerations in choosing one and not the other? If speed and scalability is our main criteria, which one should we use? We have looked around and it seems that there are more websites that use Python [i.e : Quora, digg, reddit, bitbucket and disqus] than Java. Based on that, can we say that Python is more suitable for internet applications where speed and scalability is the main criteria? However we have browsed around and found some comments saying that Java is actually faster than Python. Thank you for your insights.

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  • Python class representation under the hood

    - by decentralised
    OK, here is a simple Python class: class AddSomething(object): __metaclass__ = MyMetaClass x = 10 def __init__(self, a): self.a = a def add(self, a, b): return a + b We have specified a metaclass, and that means we could write something like this: class MyMetaClass(type): def __init__(cls, name, bases, cdict): # do something with the class Now, the cdict holds a representation of AddSomething: AddSomething = type('AddSomething', (object,), {'x' : 10, '__init__': __init__, 'add': add}) So my question is simple, are all Python classes represented in this second format internally? If not, how are they represented? EDIT - Python 2.7

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  • Why was Python's popularity so sudden? [closed]

    - by Eric Wilson
    Python first appeared in 1991, but it was somewhat unknown until 2004, if the TIOBE rankings quantify anything meaningful. What happened? What caused the interest in this 13 year old language to go through the roof? Is there a reason that Python wasn't considered a real competitor to Perl in its first decade of existence? Is there a reason that Python didn't continue in relative obscurity for another ten years? I personally think that Python is a very nice language, and I'm glad that I'm not the only one. But it doesn't have corporate backing or a killer feature that would explain a sudden rise to relevance. Does anyone know the story?

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  • Django as Python extension?

    - by NoobDev4iPhone
    I come from php community and just started learning Python. I have to create server-side scripts that manipulate databases, files, and send emails. Some of it I found hard to do in python, comparing to php, like sending emails and querying databases. Where in php you have functions like mysql_query(), or email(), in python you have to write whole bunch of code. Recently I found Django, and my question is: is it a good framework for network-oriented scripts, instead of using it as a web-framework?

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  • Making Python scripts work on MAMP

    - by Ravi Teja
    Hello All Python Pro's , I'm using mamp server for testing out all my web pages. I'm new to python. I'm able to run a script in python interpreter that will normally print a hello world. print "Hello World!" So i used the same line in a file with name test.py . So how should I run this on web. As am new to python, i tried some normal things, placing test.py in /htdocs/cgi-bin/ and trying to open it. But it says forbidden page. Anyone please help me making this work. Thanks

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  • Python: Future as a major programming language?

    - by chrisw
    After reading some Python material and seeing some Python code a few years back I decided to give it a whirl. I decided to start with Python to solve the problems on Project Euler and was throughly impressed with the language. Since then I've went on to learn Django, and now use it primarily for my web applications. I would love to have a career programming in this language, however I fear the future of the language is currently in a state of uncertainness. With Google and other major companies embracing it there may be some hope, what are your thoughts on Python, do you see many job opportunities out there?

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  • Python platform

    - by LazyTiberius
    I'm looking for a python platform or environment. I'm looking for something like or similar to easyphp ou xampp for try and learn some cms. i've find mezzanine cms http://mezzanine.jupo.org/ and skeletonz http://orangoo.com/skeletonz/ usually i use and know apache environment. But python is new for me. i'm a noob with this 2 cms (mezzanine and skeletonz). My configuration os is windows 7 and windows 8 i need something easy to simulate a python environment hosting Thank all for your help

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  • Python: Future as a major programming language?

    - by chrisw
    After reading some Python material and seeing some Python code a few years back I decided to give it a whirl. I decided to start with Python to solve the problems on ProjectEuler.net and was throughly impressed with the language. Since then I've went on to learn Django, and now use it primarily for my web applications. I would love to have a career programming in this language, however I fear the future of the language is currently in a state of uncertainness. With Google and other major companies embracing it there may be some hope, what are your thoughts on Python, do you see many job opportunities out there?

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  • dictionary of lists of dictionaries in python

    - by Andy
    I'm a perl scripter working in python and need to know a way to do the following perl in python. $Hash{$key1}[$index_value]{$key2} = $value; I have seen the stackoverflow question here: List of dictionaries, in a dictionary - in Python I still don't understand what self.rules is doing or if it works for my solution. My data will be coming from files, and will I will be using regexes to capture to temporary variables until ready to store in the data structure. If you need to ask, the order related to the $index_value is important and would like to be maintained as an integer. Any suggestions are appreciated or if you think I need to rethink data structures with Python that would be helpful.

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  • How do I extend a python module? (python-twitter)

    - by user319045
    What are the best practices for extending a python module -- in this case I want to extend python-twitter by adding new methods to the base API class. I've looked at tweepy, and I like that as well, I just find python-twitter easier to understand and extend with the functionality I want. I have the methods written already, I'm just trying to figure out the best way to add them into the module, without changing the core.

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  • Python in command line runs the wrong version?

    - by Deflect
    I have several versions of Python installed on a Windows 7 computer. I want to run Python 2.7 by default, but for whatever reason, typing python in the command line runs Python version 2.4.5. I've tried adding C:\Python27 to my system path variable as per this question, and manually combed my path variable it to make sure Python 2.4.5 wasn't tossed in there by mistake, but that didn't fix the issue. I have to type in C:\Python27\python.exe every time I want to access the correct version of python I want. What other places can I check? How can I make the command line use the correct version of python? I also found this but it's not for windows. [EDIT] My path (separated by semicolons): C:\Program Files\Common Files\Microsoft Shared\Windows Live; C:\Program Files (x86)\Common Files\Microsoft Shared\Windows Live; C:\Windows\system32; C:\Windows; C:\Windows\System32\Wbem; C:\Windows\System32\WindowsPowerShell\v1.0\; C:\Program Files\Dell\DW WLAN Card\Driver; C:\Program Files (x86)\Common Files\Roxio Shared\DLLShared\; C:\Program Files (x86)\Windows Live\Shared; c:\Program Files (x86)\Microsoft SQL Server\100\Tools\Binn\; c:\Program Files\Microsoft SQL Server\100\Tools\Binn\; c:\Program Files\Microsoft SQL Server\100\DTS\Binn\; C:\Program Files\TortoiseGit\bin; C:\Program Files\Java\jdk1.6.0_26\bin; C:\Program Files\Java\jdk1.6.0_21 ; C:\Program Files\IVI Foundation\VISA\Win64\Bin\; C:\Program Files (x86)\IVI Foundation\VISA\WinNT\Bin\; C:\Program Files (x86)\IVI Foundation\VISA\WinNT\Bin; C:\Program Files\WPIJavaCV\OpenCV_2.2.0\bin; C:\Program Files (x86)\LilyPond\usr\bin; C:\Program Files\TortoiseSVN\bin; C:\Program Files (x86)\doxygen\bin; C:\Program Files (x86)\Graphviz 2.28\bin; C:\Users\Michael\bin\Misc\cppcheck\; C:\Program Files (x86)\Git\cmd; C:\Python27\python.exe; C:\Ruby192\bin; C:\Users\Michael\AppData\Roaming\cabal\bin; C:\Python27\; [EDIT 2] Running python spews this out: 'import site' failed; used -v for traceback Python 2.4.5 (#1, Jul 22 2011, 02:01:04) [GCC 4.1.1] on mingw32 Type "help", "copyright", "credits" or "license" for more information. >>> ...and running python --version (as suggested below) seems to be an unrecognized option. (I also tried running python -v, and it appears that Python 2.4 is trying to import libraries from C:\Python27\Lib, and failed due to a syntax error when it encountered a with statement, which was added in later version, I think) Also, I'm not sure if it's significant or not, but the above python version says something about GCC and mingw32, while running C:\python27\python.exe shows this: Python 2.7.2 (default, Jun 12 2011, 15:08:59) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>>>

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  • Does Google Maps API v3 allow larger zoom values ?

    - by Dr1Ku
    If you use the satellite GMapType using this Google-provided example in v3 of the API, the maximum zoom level has a scale of 2m / 10ft , whereas using the v2 version of another Google-provided example (had to use another one since the control-simple doesn't have the scale control) yields the maximum scale of 20m / 50ft. Is this a new "feature" of v3 ? I have to mention that I've tested the examples in the same GLatLng regions - so my guess is that tile detail level doesn't influence it, am I mistaken ? As mentioned in another question, v3 is to be considered of very Labs-y/beta quality, so use in production should be discouraged for the time being. I've been drawn to the subject since I have to "increase the zoom level of a GMap", the answers here seem to suggest using GTileLayer, and I'm considering GMapCreator, although this will involve some effort. What I'm trying to achieve is to have a larger zoom level, a scale of 2m / 10ft would be perfect, I have a map where the tiles aren't that hi-res and quite a few markers. Seeing that the area doesn't have hi-res tiles, the distance between the markers is really tiny, creating some problematic overlapping. Or better yet, how can you create a custom Map which allows higher zoom levels, as by the Google Campus, where the 2m / 10ft scale is achieved, and not use your own tileserver ? I've seen an example on a fellow Stackoverflower's GMaps sandbox , where the tiles are manually created based on the zoom level. I don't think I'm making any more sense, so I'm just going to end this big question here, I've been wondering around trying to find a solution for hours now. Hope that someone comes to my aid though ! Thank you in advance !

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  • How to install suggested packages in apt-get

    - by Alaa Ali
    EDIT: I solved my issue. I will answer my own question, but in 5 hours because I don't have permission now. I know the question has been asked before, but please hear me out. So I wanted to install screenlets. I ran sudo apt-get install screenlets, and this is what I got: The following extra packages will be installed: libart-2.0-2 libbonobo2-0 libbonobo2-common libbonoboui2-0 libbonoboui2-common libgnome2-0 libgnomecanvas2-0 libgnomecanvas2-common libgnomeui-0 libgnomeui-common libtidy-0.99-0 python-beautifulsoup python-evolution python-feedparser python-gmenu python-gnome2 python-numpy python-pyorbit python-rsvg python-tz python-utidylib screenlets-pack-basic Suggested packages: libbonobo2-bin python-gnome2-doc python-numpy-doc python-numpy-dbg python-nose python-dev gfortran python-pyorbit-dbg screenlets-pack-all python-dcop Recommended packages: python-numeric python-gnome2-extras The following NEW packages will be installed: libart-2.0-2 libbonobo2-0 libbonobo2-common libbonoboui2-0 libbonoboui2-common libgnome2-0 libgnomecanvas2-0 libgnomecanvas2-common libgnomeui-0 libgnomeui-common libtidy-0.99-0 python-beautifulsoup python-evolution python-feedparser python-gmenu python-gnome2 python-numpy python-pyorbit python-rsvg python-tz python-utidylib screenlets screenlets-pack-basic 0 upgraded, 23 newly installed, 0 to remove and 2 not upgraded. People say that Recommended packages are installed by default, but they are clearly not included in the NEW packages that will be installed above. I also decided to include the Suggested packages in the installation, so I ran sudo apt-get --install-suggests install screenlets instead, but I got a HUGE list of NEW packages that will be installed; that number is precisely 0 upgraded, 944 newly installed, 0 to remove and 2 not upgraded. Should'nt I be getting only around 10 extra packages?

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  • /usr/bin/python (Python 2.4) was deleted on CentOS 5. I compiled from source but yum is still broken. How can I get everything back to the way it was?

    - by Maxwell
    I saw a lot of other questions like this but none of them answered the exact part I am having trouble with (actually installing the Python RPM). Someone on my system deleted /usr/bin/python and /usr/bin/python2.4 on my 64 bit CentOS 5.8 installation. I recompiled Python 2.4 from source, but now whenever I try to yum install anything I get the following error: [root@cerulean-OW1 ~]# yum install httpd There was a problem importing one of the Python modules required to run yum. The error leading to this problem was: No module named yum Please install a package which provides this module, or verify that the module is installed correctly. It's possible that the above module doesn't match the current version of Python, which is: 2.4 (#1, Dec 16 2012, 09:16:56) [GCC 4.1.2 20080704 (Red Hat 4.1.2-52)] If you cannot solve this problem yourself, please go to the yum faq at: http://wiki.linux.duke.edu/YumFaq I checked http://wiki.linux.duke.edu/YumFaq and it said the following: If you are getting a message that yum itself is the missing module then you probably installed it incorreclty (or installed the source rpm using make/make install). If possible, find a prebuilt rpm that will work for your system like one from Fedora or CentOS. Or, you can download the srpm and do a rpmbuild --rebuild yum*.src.rpm I tried going to http://rpm.pbone.net/index.php3/stat/4/idpl/17838875/dir/centos_5/com/python-2.4.3-46.el5.x86_64.rpm.html to install Python, which resulted in the following error: [root@cerulean-OW1 ~]# rpm -Uvh python-2.4.3-46.el5.x86_64.rpm error: Failed dependencies: python-libs-x86_64 = 2.4.3-46.el5 is needed by python-2.4.3-46.el5.x86_64 So I tried installing python-libs-x86_64, which resulted in the following: [root@cerulean-OW1 ~]# rpm -Uvh python-libs-2.4.3-46.el5_8.2.x86_64.rpm warning: python-libs-2.4.3-46.el5_8.2.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID 192a7d7d Preparing... ########################################### [100%] package python-libs-2.4.3-46.el5_8.2.x86_64 is already installed file /usr/lib64/libpython2.4.so.1.0 from install of python-libs-2.4.3-46.el5_8.2.x86_64 conflicts with file from package python-libs-2.4.3-46.el5_8.2.x86_64

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  • mysql-python on Snow Leopard with MySQL 64-bit

    - by Derek Reynolds
    Can't seem to get mysql-python to work on Snow Leopard for the life of me. Currently using the default version of python that ships with Snow Leopard (python 2.6.1). Installed MySQL 5.1.45 x86_64. I download the source for mysql-python http://sourceforge.net/projects/mysql-python/ and compile with the following commands: tar xzf MySQL-python-1.2.3c1.tar.gz cd MySQL-python-1.2.3c1 ARCHFLAGS='-arch x86_64' python setup.py build ARCHFLAGS='-arch x86_64' python setup.py install And am getting the following error when I try to import: Python 2.6.1 (r261:67515, Jul 7 2009, 23:51:51) [GCC 4.2.1 (Apple Inc. build 5646)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import MySQLdb Traceback (most recent call last): File "<stdin>", line 1, in <module> File "build/bdist.macosx-10.6-universal/egg/MySQLdb/__init__.py", line 19, in <module> File "build/bdist.macosx-10.6-universal/egg/_mysql.py", line 7, in <module> File "build/bdist.macosx-10.6-universal/egg/_mysql.py", line 6, in __bootstrap__ ImportError: dlopen(/Users/derek/.python-eggs/MySQL_python-1.2.3c1-py2.6-macosx-10.6-universal.egg-tmp/_mysql.so, 2): no suitable image found. Did find: /Users/derek/.python-eggs/MySQL_python-1.2.3c1-py2.6-macosx-10.6-universal.egg-tmp/_mysql.so: mach-o, but wrong architecture Any ideas? Or the best route for starting over.

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  • To install Markdown's extensions by Python

    - by Masi
    The installation notes (git://gitorious.org/python-markdown/mainline.git) say in the file using_as_module.txt One of the parameters that you can pass is a list of Extensions. Extensions must be available as python modules either within the markdown.extensions package or on your PYTHONPATH with names starting with mdx_, followed by the name of the extension. Thus, extensions=['footnotes'] will first look for the module markdown.extensions.footnotes, then a module named mdx_footnotes. See the documentation specific to the extension you are using for help in specifying configuration settings for that extension. I put the folder "extensions" to ~/bin/python/ such that my PYTHONPATH is the following export PYTHONPATH=/Users/masi/bin/python/:/opt/local/Library/Frameworks/Python.framework/Versions/2.6/ The instructions say that I need to import the addons such that import markdown import <module-name> However, I cannot see any module in my Python. This suggests me that the extensions are not available as "python modules - - on [my] PYTHONPATH with names starting with mdx_ - -." How can you get Markdown's extensions to work? 2nd attempt I run at ~/bin/markdown git clone git://gitorious.org/python-markdown/mainline.git python-markdown cd python-markdown python setup.py install I put the folder /Users/masi/bin/markdown/python-markdown/build to my PATH because the installation message suggests me that is the new location of the extensions. I have the following in a test markdown -document [TOC] -- headings here with # -format --- However, I do not get the table of contents. This suggests me that we need to somehow activate the extensions when we compile by the markdown.py -script. **The problem returns to my first quoted text which I is rather confusing to me.

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  • fatal error 'stdio.h' Python 2.7 on Mc OS X 10.7.5 [closed]

    - by DjangoRocks
    I have this weird issue on my Mac OS X 10.7.5 /Library/Frameworks/Python.framework/Versions/2.7/include/python2.7/Python.h:33:10: fatal error: 'stdio.h' file not found What caused the above error? This error has been bugging me and i can't install mysql-python as i'm stuck with this step. I'm using Python 2.7.3. Things like Google App Engine ( python ), python script, tornado generally works on my mac. But not mysql-python. I've install MySQL using the dmg image and have copied the mysql folder to /usr/local/ How do i fix this? ======UPDATE====== I've ran the command, and tried to install mysql-python by running sudo python setup.py install. But received the following: running install running bdist_egg running egg_info writing MySQL_python.egg-info/PKG-INFO writing top-level names to MySQL_python.egg-info/top_level.txt writing dependency_links to MySQL_python.egg-info/dependency_links.txt writing MySQL_python.egg-info/PKG-INFO writing top-level names to MySQL_python.egg-info/top_level.txt writing dependency_links to MySQL_python.egg-info/dependency_links.txt reading manifest file 'MySQL_python.egg-info/SOURCES.txt' reading manifest template 'MANIFEST.in' writing manifest file 'MySQL_python.egg-info/SOURCES.txt' installing library code to build/bdist.macosx-10.6-intel/egg running install_lib running build_py copying MySQLdb/release.py -> build/lib.macosx-10.6-intel-2.7/MySQLdb running build_ext gcc-4.2 not found, using clang instead building '_mysql' extension clang -fno-strict-aliasing -fno-common -dynamic -g -O2 -DNDEBUG -g -O3 -Dversion_info=(1,2,4,'rc',5) -D__version__=1.2.4c1 -I/usr/local/mysql/include -I/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c _mysql.c -o build/temp.macosx-10.6-intel-2.7/_mysql.o -Os -g -fno-common -fno-strict-aliasing -arch x86_64 In file included from _mysql.c:29: /Library/Frameworks/Python.framework/Versions/2.7/include/python2.7/Python.h:33:10: fatal error: 'stdio.h' file not found #include <stdio.h> ^ 1 error generated. error: command 'clang' failed with exit status 1 What other possible ways can i fix it? thanks! Best Regards.

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  • Can't seem to get python to work

    - by Justin Johnson
    I'm just starting out in Python. The Python interpreter works from the command line (I have 2.4.3), but I can't seem to get Apache to execute Python scripts. All I end up with is a blank screen and nothing in the Apache error logs. I enabled Python via the Plesk control panel. Here's the snippet that was generated in the httpd.include: <Files ~ (\.py$)> SetHandler python-program PythonHandler mod_python.cgihandler </Files> My test script is one of the examples that comes with the Python downloads at http://python.org/download/ #!/usr/local/bin/python """CGI test 1 - check server setup.""" # Until you get this to work, your web server isn't set up right or # your Python isn't set up right. # If cgi0.sh works but cgi1.py doesn't, check the #! line and the file # permissions. The docs for the cgi.py module have debugging tips. print("Content-type: text/html") print() print("<h1>Hello world</h1>") print("<p>This is cgi1.py") That wasn't working, so I changed #!/usr/local/bin/python to #!/usr/bin/python which is what which python tells me but the results were the same. Like I said, I'm ending up with a blank page. No errors that I know of, unless I'm checking the wrong error log (I'm checking the Apache error log). I'm on a MediaTemple (dv) running CentOS.

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  • Easy_install the wrong version of python modules (Mac OS)

    - by user73250
    I installed Python 2.7 on my Mac. When typing "python" in terminal, it shows: $ python Python 2.7 (r27:82508, Jul 3 2010, 20:17:05) [GCC 4.0.1 (Apple Inc. build 5493)] on darwin Type "help", "copyright", "credits" or "license" for more information. The Python version is correct here. But when I try to easy_install some modules. The system will install the modules with python version 2.6 which are not able be imported to Python 2.7. And of course I can not do the functions I need in my code. Here's an example of easy_install graphy: $ easy_install graphy Searching for graphy Reading pypi.python.org/simple/graphy/ Reading http://code.Google.com/p/graphy/ Best match: Graphy 1.0.0 Downloading http://pypi.python.org/packages/source/G/Graphy/Graphy- 1.0.0.tar.gz#md5=390b4f9194d81d0590abac90c8b717e0 Processing Graphy-1.0.0.tar.gz Running Graphy-1.0.0/setup.py -q bdist_egg --dist-dir /var/folders/fH/fHwdy4WtHZOBytkg1nOv9E+++TI/-Tmp-/easy_install-cFL53r/Graphy-1.0.0/egg-dist-tmp-YtDCZU warning: no files found matching '*.tmpl' under directory 'graphy' warning: no files found matching '*.txt' under directory 'graphy' warning: no files found matching '*.h' under directory 'graphy' warning: no previously-included files matching '*.pyc' found under directory '.' warning: no previously-included files matching '*~' found under directory '.' warning: no previously-included files matching '*.aux' found under directory '.' zip_safe flag not set; analyzing archive contents... graphy.all_tests: module references __file__ Adding Graphy 1.0.0 to easy-install.pth file Installed /Library/Python/2.6/site-packages/Graphy-1.0.0-py2.6.egg Processing dependencies for graphy Finished processing dependencies for graphy So it installs graphy for Python 2.6. Can someone help me with it? I just want to set my default easy_install Python version to 2.7.

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  • Kernel api's or using api's in the kernel

    - by user513647
    Hello everybody I'd like to know if and how I can access api calls inside the kernel. I need them to preform several integrity checks on a program of mine running in user mode. But I don't know how I can access the api's and funcions required to do so. Does anybody know how to obtain the process id of my user mode proces? and how to access all it's memory to preform the check? Thanks in advance ps: My I'm on a windows xp machine

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  • API Message Localization

    - by Jesse Taber
    In my post, “Keep Localizable Strings Close To Your Users” I talked about the internationalization and localization difficulties that can arise when you sprinkle static localizable strings throughout the different logical layers of an application. The main point of that post is that you should have your localizable strings reside as close to the user-facing modules of your application as possible. For example, if you’re developing an ASP .NET web forms application all of the localizable strings should be kept in .resx files that are associated with the .aspx views of the application. In this post I want to talk about how this same concept can be applied when designing and developing APIs. An API Facilitates Machine-to-Machine Interaction You can typically think about a web, desktop, or mobile application as a collection “views” or “screens” through which users interact with the underlying logic and data. The application can be designed based on the assumption that there will be a human being on the other end of the screen working the controls. You are designing a machine-to-person interaction and the application should be built in a way that facilitates the user’s clear understanding of what is going on. Dates should be be formatted in a way that the user will be familiar with, messages should be presented in the user’s preferred language, etc. When building an API, however, there are no screens and you can’t make assumptions about who or what is on the other end of each call. An API is, by definition, a machine-to-machine interaction. A machine-to-machine interaction should be built in a way that facilitates a clear and unambiguous understanding of what is going on. Dates and numbers should be formatted in predictable and standard ways (e.g. ISO 8601 dates) and messages should be presented in machine-parseable formats. For example, consider an API for a time tracking system that exposes a resource for creating a new time entry. The JSON for creating a new time entry for a user might look like: 1: { 2: "userId": 4532, 3: "startDateUtc": "2012-10-22T14:01:54.98432Z", 4: "endDateUtc": "2012-10-22T11:34:45.29321Z" 5: }   Note how the parameters for start and end date are both expressed as ISO 8601 compliant dates in UTC. Using a date format like this in our API leaves little room for ambiguity. It’s also important to note that using ISO 8601 dates is a much, much saner thing than the \/Date(<milliseconds since epoch>)\/ nonsense that is sometimes used in JSON serialization. Probably the most important thing to note about the JSON snippet above is the fact that the end date comes before the start date! The API should recognize that and disallow the time entry from being created, returning an error to the caller. You might inclined to send a response that looks something like this: 1: { 2: "errors": [ {"message" : "The end date must come after the start date"}] 3: }   While this may seem like an appropriate thing to do there are a few problems with this approach: What if there is a user somewhere on the other end of the API call that doesn’t speak English?  What if the message provided here won’t fit properly within the UI of the application that made the API call? What if the verbiage of the message isn’t consistent with the rest of the application that made the API call? What if there is no user directly on the other end of the API call (e.g. this is a batch job uploading time entries once per night unattended)? The API knows nothing about the context from which the call was made. There are steps you could take to given the API some context (e.g.allow the caller to send along a language code indicating the language that the end user speaks), but that will only get you so far. As the designer of the API you could make some assumptions about how the API will be called, but if we start making assumptions we could very easily make the wrong assumptions. In this situation it’s best to make no assumptions and simply design the API in such a way that the caller has the responsibility to convey error messages in a manner that is appropriate for the context in which the error was raised. You would work around some of these problems by allowing callers to add metadata to each request describing the context from which the call is being made (e.g. accepting a ‘locale’ parameter denoting the desired language), but that will add needless clutter and complexity. It’s better to keep the API simple and push those context-specific concerns down to the caller whenever possible. For our very simple time entry example, this can be done by simply changing our error message response to look like this: 1: { 2: "errors": [ {"code": 100}] 3: }   By changing our error error from exposing a string to a numeric code that is easily parseable by another application, we’ve placed all of the responsibility for conveying the actual meaning of the error message on the caller. It’s best to have the caller be responsible for conveying this meaning because the caller understands the context much better than the API does. Now the caller can see error code 100, know that it means that the end date submitted falls before the start date and take appropriate action. Now all of the problems listed out above are non-issues because the caller can simply translate the error code of ‘100’ into the proper action and message for the current context. The numeric code representation of the error is a much better way to facilitate the machine-to-machine interaction that the API is meant to facilitate. An API Does Have Human Users While APIs should be built for machine-to-machine interaction, people still need to wire these interactions together. As a programmer building a client application that will consume the time entry API I would find it frustrating to have to go dig through the API documentation every time I encounter a new error code (assuming the documentation exists and is accurate). The numeric error code approach hurts the discoverability of the API and makes it painful to integrate with. We can help ease this pain by merging our two approaches: 1: { 2: "errors": [ {"code": 100, "message" : "The end date must come after the start date"}] 3: }   Now we have an easily parseable numeric error code for the machine-to-machine interaction that the API is meant to facilitate and a human-readable message for programmers working with the API. The human-readable message here is not intended to be viewed by end-users of the API and as such is not really a “localizable string” in my opinion. We could opt to expose a locale parameter for all API methods and store translations for all error messages, but that’s a lot of extra effort and overhead that doesn’t add a lot real value to the API. I might be a bit of an “ugly American”, but I think it’s probably fine to have the API return English messages when the target for those messages is a programmer. When resources are limited (which they always are), I’d argue that you’re better off hard-coding these messages in English and putting more effort into building more useful features, improving security, tweaking performance, etc.

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