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How to extract the n-th elements from a list of tuples?
... *list in arguments to create a parameter list for a function...
Note: In Python3, zip returns an iterator, so instead use list(zip(*elements)) to return a list of tuples.
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Python Pandas: Get index of rows which column matches certain value
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Get path from open file in Python
...g with it, then you can do that in the following conventional way using os Python module.
>>> import os
>>> f = open('/Users/Desktop/febROSTER2012.xls')
>>> os.path.dirname(f.name)
>>> '/Users/Desktop/'
This way you can get hold of the directory structure.
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python pandas: apply a function with arguments to a series
I want to apply a function with arguments to a series in python pandas:
4 Answers
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Add up a column of numbers at the Unix shell
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python3 -c"import os; print(sum(os.path.getsize(f) for f in open('files.txt').read().split()))"
Or if you just want to sum the numbers, pipe into:
python3 -c"import sys; print(sum(int(x) for x in sys.stdin))"
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How can strings be concatenated?
How to concatenate strings in python?
7 Answers
7
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Why use argparse rather than optparse?
I noticed that the Python 2.7 documentation includes yet another command-line parsing module. In addition to getopt and optparse we now have argparse .
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what does the __file__ variable mean/do?
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When a module is loaded from a file in Python, __file__ is set to its path. You can then use that with other functions to find the directory that the file is located in.
Taking your examples one at a time:
A = os.path.join(os.path.dirname(__file__), '..')
# A is...
Filter dict to contain only certain keys?
...Uses dictionary comprehension.
If you use a version which lacks them (ie Python 2.6 and earlier), make it dict((your_key, old_dict[your_key]) for ...). It's the same, though uglier.
Note that this, unlike jnnnnn's version, has stable performance (depends only on number of your_keys) for old_dicts...
How Pony (ORM) does its tricks?
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Pony ORM author is here.
Pony translates Python generator into SQL query in three steps:
Decompiling of generator bytecode and rebuilding generator AST
(abstract syntax tree)
Translation of Python AST into "abstract SQL" -- universal
list-based representation of a...