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Why is “if not someobj:” better than “if someobj == None:” in Python?
...a __nonzero__ special method (as do numeric built-ins, int and float), it calls this method. It must either return a bool value which is then directly used, or an int value that is considered False if equal to zero.
Otherwise, if the object has a __len__ special method (as do container built-ins, li...
How to save all the variables in the current python session?
I want to save all the variables in my current python environment. It seems one option is to use the 'pickle' module. However, I don't want to do this for 2 reasons:
...
Inheritance and Overriding __init__ in python
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The book is a bit dated with respect to subclass-superclass calling. It's also a little dated with respect to subclassing built-in classes.
It looks like this nowadays:
class FileInfo(dict):
"""store file metadata"""
def __init__(self, filename=None):
super(FileInfo,...
How to find the size of localStorage
...ly developing a site that will make use of HTML5's localStorage. I've read all about the size limitations for different browsers. However, I haven't seen anything on how to find out the current size of a localStorage instance. This question seems to indicate that JavaScript doesn't have a built in...
Is it ever advantageous to use 'goto' in a language that supports loops and functions? If so, why?
...o this already):
Cleanly exiting a function
Often in a function, you may allocate resources and need to exit in multiple places. Programmers can simplify their code by putting the resource cleanup code at the end of the function, and all "exit points" of the function would goto the cleanup label....
Define a lambda expression that raises an Exception
...ur goal is to avoid a def, this obviously doesn't cut it. It does, however allow you to conditionally raise exceptions, e.g.:
y = lambda x: 2*x if x < 10 else raise_(Exception('foobar'))
Alternatively you can raise an exception without defining a named function. All you need is a strong stom...
What does the “yield” keyword do?
... list, you can read its items one by one. Reading its items one by one is called iteration:
>>> mylist = [1, 2, 3]
>>> for i in mylist:
... print(i)
1
2
3
mylist is an iterable. When you use a list comprehension, you create a list, and so an iterable:
>>> mylist = [...
How to automatically generate a stacktrace when my program crashes
... the GCC compiler. When my C++ program crashes I would like it to automatically generate a stacktrace.
28 Answers
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Check if $_POST exists
...sts and if it does, print it inside another string, if not, don't print at all.
14 Answers
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Byte order mark screws up file reading in Java
...va. Some of the files may have a byte order mark in the beginning, but not all. When present, the byte order gets read along with the rest of the first line, thus causing problems with string compares.
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