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Why return NotImplemented instead of raising NotImplementedError
...
It's because __lt__() and related comparison methods are quite commonly used indirectly in list sorts and such. Sometimes the algorithm will choose to try another way or pick a default winner. Raising an exception would break out of the s...
Checking images for similarity with OpenCV
...e the L2 relative error between images.
double errorL2 = norm( A, B, CV_L2 );
// Convert to a reasonable scale, since L2 error is summed across all pixels of the image.
double similarity = errorL2 / (double)( A.rows * A.cols );
return similarity;
}
else {
//Images have a differen...
How to list all functions in a Python module?
...n example with inspect:
from inspect import getmembers, isfunction
from my_project import my_module
functions_list = [o for o in getmembers(my_module) if isfunction(o[1])]
getmembers returns a list of (object_name, object_type) tuples.
You can replace isfunction with any of the other isXXX func...
“Private” (implementation) class in Python
...
Use a single underscore prefix:
class _Internal:
...
This is the official Python convention for 'internal' symbols; "from module import *" does not import underscore-prefixed objects.
Edit: Reference to the single underscore convention
...
What does it mean if a Python object is “subscriptable” or not?
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It basically means that the object implements the __getitem__() method. In other words, it describes objects that are "containers", meaning they contain other objects. This includes strings, lists, tuples, and dictionaries.
...
Commenting in a Bash script inside a multiline command
...utput MYSQLDUMP file
cat ${MYSQLDUMP} | \
# simplify the line
sed '/created_at/d' | \
# create some newlines
tr ",;" "\n" | \
# use some sed magic
sed -e 's/[asbi]:[0-9]*[:]*//g' -e '/^[{}]/d' -e 's/""//g' -e '/^"{/d' | \
# more magic
sed -n -e '/^"/p' -e '/^print_value$/,/^option_id$/p' | \
# even ...
Can you give a Django app a verbose name for use throughout the admin?
... the 1.8 docs (and current docs),
New applications should avoid default_app_config. Instead they should require the dotted path to the appropriate AppConfig subclass to be configured explicitly in INSTALLED_APPS.
Example:
INSTALLED_APPS = [
# ...snip...
'yourapp.apps.YourAppConfig',
]...
How to get a reference to a module inside the module itself?
...
import sys
current_module = sys.modules[__name__]
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Chrome Extension how to send data from content script to popup.html
... the info.
Directory structure:
root-directory/
|_____img
|_____icon19.png
|_____icon38.png
|_____manifest.json
|_____background.js
|_____content.js
|_____popup.js
|_____popup.html
...
How to sort two lists (which reference each other) in the exact same way
... of 10000 random ints): %timeit index = range(len(l1)); index.sort(key=l1.__getitem__); map(l1.__getitem__, index); map(l2.__getitem__, index) 100 loops, best of 3: 8.04 ms per loop (vs 9.17 ms, 9.07 ms for senderle's timits)
– Quantum7
Aug 12 '13 at 21:35
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