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What are some (concrete) use-cases for metaclasses?
... B(A):
... pass
...
>>> models
{'A': <__main__.A class at 0x...>,
'B': <__main__.B class at 0x...>}
This can also be done with class decorators:
models = {}
def model(cls):
models[cls.__name__] = cls
return cls
@model
class A(object):
pass
Or with an expl...
Get a list of distinct values in List
...
Notes.Select(x => x.Author).Distinct();
This will return a sequence (IEnumerable<string>) of Author values -- one per unique value.
share
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multiple prints on the same line in Python
...can use the print statement to do this without importing sys.
def install_xxx():
print "Installing XXX... ",
install_xxx()
print "[DONE]"
The comma on the end of the print line prevents print from issuing a new line (you should note that there will be an extra space at the end of the out...
Monad in plain English? (For the OOP programmer with no FP background)
...stem which lets you take a type and turn it into a more special type. For example, in C# consider Nullable<T>. This is an amplifier of types. It lets you take a type, say int, and add a new capability to that type, namely, that now it can be null when it couldn't before.
As a second example, ...
Turn a string into a valid filename?
...look at the Django framework for how they create a "slug" from arbitrary text. A slug is URL- and filename- friendly.
The Django text utils define a function, slugify(), that's probably the gold standard for this kind of thing. Essentially, their code is the following.
def slugify(value):
""...
Canvas width and height in HTML5
Is it possible to fix the width and height of an HTML5 canvas element?
4 Answers
4
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__getattr__ on a module
...ibute__. Dunder methods had previously worked on modules - you could, for example, use a module as a context manager simply by defining __enter__ and __exit__, before those tricks broke.
Recently some historical features have made a comeback, the module __getattr__ among them, and so the existing ...
How can I post data as form data instead of a request payload?
...he code below, the AngularJS $http method calls the URL, and submits the xsrf object as a "Request Payload" (as described in the Chrome debugger network tab). The jQuery $.ajax method does the same call, but submits xsrf as "Form Data".
...
Where can I find “make” program for Mac OS X Lion?
Just upgraded my computer to Mac OS X Lion and went to terminal and typed "make" but it says:
-bash: make: command not found
...
When to use nested classes and classes nested in modules?
... name of the class Wheel vs. Car::Wheel. This difference in name can make explicit to programmers that the Car::Wheel class can only represent a car wheel, as opposed to a general wheel. Nesting class definitions in Ruby is a matter of preference, but it serves a purpose in the sense that it more st...