Where can i find good practice python problems with solutions?
I'm looking for detailed practice problems that are designed with a coding purpose in mind.
I've been using Pythonfor quite a while now, and I'm still unsure as to why you would subclass from object. What is the difference between this:
class MyClass():
pass
And this:
class MyClass(object):
pass
As far as I understand, object is the base class for all classes and the subclassing is implied. Do you get anything from explicitly subclassing from it? What is the most "Pythonic" thing to do?
In Windows the Dropbox client uses python25.dll and the MS C runtime libraries (msvcp71.dll, etc). On OS X the Python code is compiled bytecode (pyc).
My guess is they are using a common library they have written then just have to use different hooks for the different platforms.
What method of development is this? It clearly isn't IronPython or PyObjC. This paradigm is so appealing to me, but my CS foo and Google foo are failing me.
I have a list of elements, and each element consists of four seperate values that are seperated by tabs:
['A\tB\tC\tD', 'Q\tW\tE\tR', etc.]
What I want is to create a larger list without the tabs, so that each value is a seperate element:
['A', 'B', 'C', 'D', 'Q', 'W', 'E', 'R', etc.]
How can I do that in Python? I need it for my coursework, due tonight (midnight GMT) and I'm completely stumped.
I want to start using Pythonfor small projects but the fact that a misplaced tab or indent can throw a compile error is really getting on my nerves. Is there some type of setting to turn this off?
I'm currently using NotePad++. Is there maybe an IDE that would take care of the tabs and indenting?
I have a file that I need to "protect" so that it cannot be copied! I am using Python on Windows XP.
I think it may just be changing file permissions??
In Perl, I would write:
$x = "abbbc";
$x =~ s/(b+)/z/;
print "Replaced $1 and ended up with $x\n";
# "Replaced bbb and ended up with azc"
How do I do this in Python -- do a regular-expression string replacement and record what it was that got replaced?
Is there a way in python without wrapping a function call like following?
from sys import stdout
from copy import copy
tempstdout = copy(stdout)
stdout = file("trash",w)
foo()
stdout = tempstdout
That way works but appears to be terribly inefficient. There has to be a better way... I would appreciate any insight I can get into this.
All the Python built-ins are subclasses of object and I come across many user-defined classes which are too. Why? What is the purpose of the class object? It's just an empty class, right?
I am trying to add some security to my computer at home and would like to have a copy of all Yahoo! IMs sent to me. I am using Python 2.6 on Windows.
I would also like to have every URL in Internet Explorer sent to me.
On a fresh mac os x 10.8 install, i've Quantum GIS Installed from Kingchaos binaries and running fine. I'm trying to develop a plugin for QGIS, and using Plugin Builder.
The skel that Plugin Builder, produces, should work off-the-shelf, but it does not compile using the makefile. Somewhere python can't find (pyuic.py), and it searches for (/Users/kyngchaos/...), path. This user does not exist on my system:(
Here are my ENVS on .profile:
export PATH=/Library/Frameworks/GDAL.framework/Programs:$PATH
export PYTHONPATH=/Applications/QGIS.app/Contents/Resources/python
export DYLD_LIBRARY_PATH="/Applications/QGIS.app/Contents/MacOS/lib:/Applications/Qgis.app/Contents/Frameworks"
export PATH="/Applications/QGIS.app/Contents/MacOS/bin:$PATH"
Here is the ouptput of make:
Arthur@teste:make
pyuic4 -o ui_teste.py ui_teste.ui
/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: can't open file '/Users/kyngchaos/Applications/qgis-python27/Applications/QGIS.app/Contents/MacOS/../Resources/python/PyQt4/uic/pyuic.py': [Errno 2] No such file or directory
make: *** [ui_teste.py] Error 2
thanks for reading.
A project that involves image processing, i.e. to calculate the angular shift of the same image when shifted by a medium of certain Refractive Index. We have to build an app that correlates the 2 images (phase/2D correlation?) and then plot using Chaco and Mayavi (2 libraries in Python).
Is there any other existing template software (FOSS) that we can base our app on, or use it as a reference?
I was wondering how to make a python script portable to both linux and windows?
One problem I see is shebang. How to write the shebang so that the script can be run on both windows and linux?
Are there other problems besides shebang that I should know?
Is the solution same for perl script?
Thanks and regards!
I'm parsing some code and want to match the doxygen comments before a function. However, because I want to match for a specific function name, getting only the immediately previous comment is giving me problems.
Is there a way to search backward through a string using the Python Regex library?
Is there a better (easier) approach that I'm missing?
Why in this millenium should Python PEP-8 specify a maximum line length of 79 characters?
Pretty much every code editor under the sun can handle longer lines. What to do with wrapping should be the choice of the content consumer, not the responsibility of the content creator.
Are there any (legitimately) good reasons for adhering to 79 characters in this age?
I am doing some prototyping for a new desktop app i am writing in Python, and i want to use SQLite and an ORM to store data.
My question is, are there any ORM libraries that support auto-generating/updating the database schema and work with SQLite?
I would like to install my python application as a command line tool that should work entirelly inside the install directory (for example C:\Python26\Lib\site-packages\application)
The problem is I would like to reffer in runtime to the submodules and resources from within the application directory three. If I install the app with [console_scripts] option the default path is the current directory. Is there a elegant way to keep the current execution path of the application to the site-packages directory?
Thanks
I usually do this in Perl:
whatever.pl
while(<>) {
#do whatever;
}
then cat foo.txt | whatever.pl
Now, I want to do this in Python. I tried sys.stdin but I have no idea how to do as I have done in Perl. How can I read the input?
Thanks.
EDIT:
Thanks, I like every single solution.
How can I find the dimensions of a matrix in Python. Len(A) returns only one variable.
Edit:
Hi Thanks.
close = dataobj.get_data(timestamps, symbols, closefield)
Is (I assume) generating a matrix of integers (less likely strings). I need to find the size of that matrix, so I can run some tests without having to iterate through all of the elements. As far as the data type goes, I assume it's an array of arrays (or list of lists).
In a python source code I stumbled upon I've seen a small b before a string like in:
b"abcdef"
I know of u prefix that means unicode and r prefix that means raw.
What does the b stand for and in which kind of source code is it useful as it seems to be exactly like a plain string without any prefix ?
I want to create a class that doesn't gives an Attribute Error on call of any method that may or may not exists:
My class:
class magic_class:
...
# How to over-ride method calls
...
Expected Output:
ob = magic_class()
ob.unknown_method()
# Prints 'unknown_method' was called
ob.unknown_method2()
# Prints 'unknown_method2' was called
Now, unknown_method and unknown_method2 doesn't actually exists in the class, but how can we intercept the method call in python ?
in python , suppose i have file data.txt . which has 6 lines of data . I want to calculate the no of lines which i am planning to do by going through each character and finding out the number of '\n' in the file . How to take one character input from the file ? Readline taken the whole line .
The question is how to write a program that measures how many times a character appears in a string in a generalizable way in python.
The code that I wrote:
def countLetters(str, ch):
count=0
index=0
for ch in str:
if ch==str[index]:
count=count+1
index=index+1
print count
when I use this function, it measures the length of the string instead of how many times the character occurs in the string. What did I do wrong? What is the right way to write this code?
The following unicode and string can exist on their own if defined explicitly:
>>> value_str='Andr\xc3\xa9'
>>> value_uni=u'Andr\xc3\xa9'
If I only have u'Andr\xc3\xa9' assigned to a variable like above, how do I convert it to 'Andr\xc3\xa9' in Python 2.5 or 2.6?
Is there Perl's YAPE::Regex::Explain alternative to python?
For example, which could do following regex
\w+=\d+|\w+='[^']+'
to explanations like this
NODE EXPLANATION
--------------------------------------------------------------------------------
\w+ word characters (a-z, A-Z, 0-9, _) (1 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
= '='
--------------------------------------------------------------------------------
\d+ digits (0-9) (1 or more times (matching
the most amount possible))
--------------------------------------------------------------------------------
| OR
--------------------------------------------------------------------------------
\w+ word characters (a-z, A-Z, 0-9, _) (1 or
more times (matching the most amount
possible))
--------------------------------------------------------------------------------
=' '=\''
--------------------------------------------------------------------------------
[^']+ any character except: ''' (1 or more times
(matching the most amount possible))
--------------------------------------------------------------------------------
' '\''