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How do I get the opposite (negation) of a Boolean in Python?
...ful if you want to use a function that requires a predicate-function or a callback.
For example map or filter:
>>> lst = [True, False, True, False]
>>> list(map(operator.not_, lst))
[False, True, False, True]
>>> lst = [True, False, True, False]
>>> list(filter...
Find which version of package is installed with pip
..., is it possible to figure out which version of a package is currently installed?
15 Answers
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What is the difference between old style and new style classes in Python?
...(x) is always <type
'instance'>.
This reflects the fact that all old-style instances, independently of
their class, are implemented with a single built-in type, called
instance.
New-style classes were introduced in Python 2.2 to unify the concepts of class and type.
A new-s...
What is the difference between “px”, “dip”, “dp” and “sp”?
...lems with dp while everything works fine with dip
– DallaRosa
Jul 4 '11 at 6:07
255
One note abou...
How to count the number of set bits in a 32-bit integer?
...Hamming Weight', 'popcount' or 'sideways addition'.
The 'best' algorithm really depends on which CPU you are on and what your usage pattern is.
Some CPUs have a single built-in instruction to do it and others have parallel instructions which act on bit vectors. The parallel instructions (like x86's ...
Google maps API V3 - multiple markers on exact same spot
...rieving a list of geo coords via JSON and popping them onto a google map. All is working well except in the instance when I have two or more markers on the exact same spot. The API only displays 1 marker - the top one. This is fair enough I suppose but would like to find a way to display them all...
How to avoid “if” chains?
...ep<X>() should evaluate only if the previous one succeeded (this is called short circuit evaluation)
executeThisFunctionInAnyCase() will be executed in any case
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How to disable and re-enable console logging in Python?
... If you wanted to only filter message below a certain log level (say, all INFO messages), you could change the second line to something like logger.setLevel(logging.WARNING)
– Hartley Brody
Jan 5 '18 at 16:48
...
How to step through Python code to help debug issues?
...
Yes! There's a Python debugger called pdb just for doing that!
You can launch a Python program through pdb by using pdb myscript.py or python -m pdb myscript.py.
There are a few commands you can then issue, which are documented on the pdb page.
Some usef...
How can I quantify difference between two images?
...s on the first image to edges on the second.
Is there noise in the image?
All sensors pollute the image with some amount of noise. Low-cost sensors have more noise. You may wish to apply some noise reduction before you compare images. Blur is the most simple (but not the best) approach here.
What k...