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Wrapping a C library in Python: C, Cython or ctypes?
I want to call a C library from a Python application. I don't want to wrap the whole API, only the functions and datatypes that are relevant to my case. As I see it, I have three choices:
...
Calculating a directory's size using Python?
...
This walks all sub-directories; summing file sizes:
import os
def get_size(start_path = '.'):
total_size = 0
for dirpath, dirnames, filenames in os.walk(start_path):
for f in filenames:
fp = os.path.join(di...
List of lists changes reflected across sublists unexpectedly
...
When you write [x]*3 you get, essentially, the list [x, x, x]. That is, a list with 3 references to the same x. When you then modify this single x it is visible via all three references to it:
x = [1] * 4
l = [x] * 3
print(f"id(x): {id(x)}")
# id(x): 1405608979...
Understanding repr( ) function in Python
...gt;>> x
'foo'
So the name x is attached to 'foo' string. When you call for example repr(x) the interpreter puts 'foo' instead of x and then calls repr('foo').
>>> repr(x)
"'foo'"
>>> x.__repr__()
"'foo'"
repr actually calls a magic method __repr__ of x, which gives the s...
What are deferred objects?
...As of jQuery 1.5, the Deferred object provides a way to register multiple callbacks into self-managed callback queues, invoke callback queues as appropriate, and relay the success or failure state of any synchronous or asynchronous function.
Deferred Methods:
deferred.done()
Add handlers to be cal...
PHP Redirect with POST data
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Generate a form on Page B with all the required data and action set to Page C and submit it with JavaScript on page load. Your data will be sent to Page C without much hassle to the user.
This is the only way to do it. A redirect is a 303 HTTP header tha...
Django TemplateDoesNotExist?
... assuming that you have the apps configured in settings.py like this:
INSTALLED_APPS = (
'appname1',
'appname2',
'appname3',
)
By default Django will load the templates under templates/ directory under every installed apps. So with your directory structure, we want to move our templat...
Application not picking up .css file (flask/python)
...need to have a 'static' folder setup (for css/js files) unless you specifically override it during Flask initialization. I am assuming you did not override it.
Your directory structure for css should be like:
/app
- app_runner.py
/services
- app.py
/templates
- mainpa...
How does collections.defaultdict work?
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Usually, a Python dictionary throws a KeyError if you try to get an item with a key that is not currently in the dictionary. The defaultdict in contrast will simply create any items that you try to access (provided of course th...
What is copy-on-write?
...gy used in computer programming. The fundamental idea is that if multiple callers ask for resources which are initially indistinguishable, you can give them pointers to the same resource. This function can be maintained until a caller tries to modify its "copy" of the resource, at which point a true...