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  • How to send Event signal through Processes - C

    - by Jamie Keeling
    Hello all! I have an application consisting of two windows, one communicates to the other and sends it a struct constaining two integers (In this case two rolls of a dice). I will be using events for the following circumstances: Process a sends data to process b, process b displays data Process a closes, in turn closing process b Process b closes a, in turn closing process a I have noticed that if the second process is constantly waiting for the first process to send data then the program will be just sat waiting, which is where the idea of implementing threads on each process occurred and I have started to implement this already. The problem i'm having is that I don't exactly have a lot of experience with threads and events so I'm not sure of the best way to actually implement what I want to do. I'm trying to work out how the other process will know of the event being fired so it can do the tasks it needs to do, I don't understand how one process that is separate from another can tell what the states the events are in especially as it needs to act as soon as the event has changed state. Thanks for any help Edit: I can only use the Create/Set/Open methods for events, sorry for not mentioning it earlier.

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  • Python: Why Does a Method Behave Differently with an Added Parameter?

    - by SteveStifler
    I have a method in a Pygame Sprite subclass, defined as such: def walk(self): """move across screen""" displacement = self.rect.move((self.move, 0)) if self.rect.left < self.area.left or self.rect.right > self.area.right: self.move = -self.move displacement = self.rect.move((self.move, 0)) self.rect = displacement I modified it, adding a parameter speed_x, and now the program is broken. def walk(self, speed_x): """move across screen""" displacement = self.rect.move((speed_x, 0)) if self.rect.left < self.area.left or self.rect.right > self.area.right: speed_x = -speed_x displacement = self.rect.move((speed_x, 0)) self.rect = displacement Before I called the method like this: def update(self): self.walk() Now I do: def update(self): self.walk(self.move) Why doesn't this work?

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  • Possible to capture the returned value from a Python list comprehension for use a condition?

    - by Joe
    I want to construct a value in a list comprehension, but also filter on that value. For example: [expensive_function(x) for x in generator where expensive_function(x) < 5] I want to avoid calling expensive_function twice per iteration. The generator may return an infinite series, and list comprehensions aren't lazily evaluated. So this wouldn't work: [y in [expensive_function(x) for x in generator where expensive_function(x)] where y < 5] I could write this another way, but it feels right for a list comprehension and I'm sure this is a common usage pattern (possible or not!).

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  • Is it possible to use 'else' in a python list comprehension?

    - by Josh
    Here is the code I was trying to turn into a list comprehension: table = '' for index in xrange(256): if index in ords_to_keep: table += chr(index) else: table += replace_with Is there a way to add the else statement to this comprehension? table = ''.join(chr(index) for index in xrange(15) if index in ords_to_keep) Also, would I be right in concluding that a list comprehension is the most efficient way to do this?

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  • How do you iterate through each email in your inbox using python?

    - by djblue2009
    I'm completely new to programming and I'm trying to build an autorespoder to send a msg to a specific email address. Using an if statement, I can check if there is an email from a certain address in the inbox and I can send an email, but if there are multiple emails from that address, how can I make a for loop to send an email for every email from that specific address. I tried to do use this as a loop: for M.search(None, 'From', address) in M.select(): but I get the error: "can't assign to function call" on that line

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  • Python fCGI + sqlAlchemy = malformed header from script. Bad header=FROM tags : index.py

    - by crgwbr
    I'm writing an Fast-CGI application that makes use of sqlAlchemy & MySQL for persistent data storage. I have no problem connecting to the DB and setting up ORM (so that tables get mapped to classes); I can even add data to tables (in memory). But, as soon as I query the DB (and push any changes from memory to storage) I get a 500 Internal Server Error and my error.log records malformed header from script. Bad header=FROM tags : index.py, when tags is the table name. Any idea what could be causing this? Also, I don't think it matters, but its a Linux development server talking to an off-site (across the country) MySQL server.

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  • Re-order list in Python to ensure it starts with check values.

    - by S_Swede
    Dear all, I'm reading in serial data using Pyserial, to populate a list of 17 values (1byte each) at a sampling rate of 256Hz. The bytes I ultimately want to use are the 5th to 8th in the list. Providing no bytes are dropped, the first two values of the stream are always the same ('165','90'). I'm getting quite a few dropped values though, and my list values are shifting, so when I read the 5th-8th bytes, they aren't the correct values. I've partially combatted this by ensuring that before the wanted segement is captured, the first few values are checked against what they should be (i.e. if mylist[0]==165 &....). This is crude but ok since the chances of these two values appearing adjacent to each other in the list elsewhere is small. The problem is that this means as soon as the bytes shift, I'm losing a load of values, until it eventually realigns. My question is: what code can I use to either: a) Force the list to realign once it has been detected that it no longer starts with 165,90. (elif....). b) Detect where '165' & '90' are (next to each other) in the list and extract the values I want in relation to their position (next but one, onwards). Thanks in advance S_S Just noticed from the related Qs that I could use mylist.append(mylist.pop(0)) multiple times until they are in the right place. Is there a better way that anyone can suggest?

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  • In Python, can I single line a for loop over iterator with an IF filter?

    - by Tal Weiss
    Silly question: I have a simple for loop followed by a simple if statement: for airport in airports: if airport.is_important: and I was wondering if I can write this as a single line somehow. So, yes, I can do this: for airport in (airport for airport in airports if airport.is_important): but it reads so silly and redundant ("for airport in airport for airport in airports..."). Is there a better way?

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  • What is the difference between type and type.__new__ in python?

    - by Jason Baker
    I was writing a metaclass and accidentally did it like this: class MetaCls(type): def __new__(cls, name, bases, dict): return type(name, bases, dict) ...instead of like this: class MetaCls(type): def __new__(cls, name, bases, dict): return type.__new__(cls, name, bases, dict) What exactly is the difference between these two metaclasses? And more specifically, what caused the first one to not work properly (some classes weren't called into by the metaclass)?

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  • What's the life-time of a thread-local value in Python?

    - by Carlos Valiente
    import threading mydata = threading.local() def run(): # When will the garbage collector be able to destroy the object created # here? After the thread exits from ``run()``? After ``join()`` is called? # Or will it survive the thread in which it was created, and live until # ``mydata`` is garbage-collected? mydata.foo = object() t = threading.Thread(target=run) t.start() t.join()

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  • How can I specify a relative path in a Python logging config file?

    - by ClaudioA
    I've the following file to config logging: [loggers] keys=root [handlers] keys = root [formatters] keys = generic # Loggers [logger_root] level = DEBUG handlers = root # Handlers [handler_root] class = handlers.RotatingFileHandler args = ("test.log", "maxBytes=1*1024*1024", "backupCount=10") level = NOTSET formatter = generic # Formatters [formatter_generic] format = %(asctime)s,%(msecs)03d %(levelname)-5.5s [%(name)s] %(message)s datefmt = %Y-%m-%d %H:%M:%S In Development this works great, but when I deploy the application test.log is trying to be written in a path in which I don't have the necessary permission. So my question is, How can I do to specify a relative path in this configuration file.

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  • how to scrawl file hosting website with scrapy in python?

    - by Veryel Hua
    Can anyone help me to figure out how to scrawl file hosting website like filefactory.com? I don't want to download all the file hosted but just to index all available files with scrapy. I have read the tutorial and docs with respect to spider class for scrapy. If I only give the website main page as the begining url I wouldn't not scrawl the whole site, because the scrawling depends on links but the begining page seems not point to any file pages. That's the problem I am thinking and any help would be appreciated!

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  • How to access a function inside a function? Python

    - by viddhart
    I am wondering how I can access a function inside another function. I saw code like this: >>> def make_adder(x): def adder(y): return x+y return adder >>> a = make_adder(5) >>> a(10) 15 So, is there another way to call the adder function? And my second question is why in the last line I call adder not adder(...)? Good explanations are much appreciated.

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  • Python appengine Query does not work when using a variable.

    - by Lloyd
    Hi, I am trying to use a fetcher method to retrieve items from my datastore. If I use the following def getItem(item_id): q = Item.all() q.filter("itemid = ", item_id) It fails because nothing is returned. If I hard code in an item like def getItem(item_id): q = Item.all() q.filter("itemid = ", 9000) it fetches just fine, and sings merrily along. I have tried every which way to get this to work. I have used result = db.GqlQuery("SELECT * FROM Item WHERE item_id = :1 LIMIT 1", title).fetch(1) to the same effect. If I hard code in a number, works fine. I have tried setting the select statement as a local string, assembling it that way, casting the int as a string, and nothing. When I output the SELECT statement to the screen, looks fine. I can cut ans paste the output into the string, and whammo, it works. Any help would be appreciated.

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  • Where is a good place/way to store Windows config files for Python scripts?

    - by thornomad
    I have a script/program I am working on that requires a configuration file (I am using ConfigParser). On linux, I will default to store these variables in ~/.myscript using the os.getenv('HOME') function. With Windows, I know I can use os.getenv('USERPROFILE') to find the User's "home" directory, however, is it a good idea to save a hidden file that way (ie, with the name .myscript)? I don't use Windows, obviously, but wanted to be smart about it for those who do. Is there a standard place/way to store these config variables on Windows?

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