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How to get first element in a list of tuples?
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From a performance point of view, in python3.X
[i[0] for i in a] and list(zip(*a))[0] are equivalent
they are faster than list(map(operator.itemgetter(0), a))
Code
import timeit
iterations = 100000
init_time = timeit.timeit('''a = [(i, u'abc') for i in ra...
Format a datetime into a string with milliseconds
...t;>>> OUTPUT >>>>
2020-05-04 10:18:32.926
Note: For Python3, print requires parentheses:
print(datetime.utcnow().strftime('%Y-%m-%d %H:%M:%S.%f')[:-3])
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Reverse / invert a dictionary mapping
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In python3, use my_map.items() instead of my_map.iteritems().
– apitsch
Apr 15 '19 at 15:02
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SQLAlchemy - Getting a list of tables
...e.table_names()) File "/Users/darshanchoudhary/.virtualenvs/services/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 2128, in table_names return self.dialect.get_table_names(conn, schema) value = value.replace(self.escape_quote, self.escape_to_quote) AttributeError: 'NoneType'...
Python 3: UnboundLocalError: local variable referenced before assignment [duplicate]
...e f to 3, so it is not a function any more.
Fortunately, it works fine in Python3 after adding the parentheses to print.
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Auto-reload browser when I save changes to html file, in Chrome?
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There is also python3 -m http.server, as well as many more for other languages/tools.
– carlwgeorge
Oct 28 '17 at 22:23
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Import Error: No module named numpy
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You can simply use
pip install numpy
Or for python3, use
pip3 install numpy
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ImportError: DLL load failed: %1 is not a valid Win32 application. But the DLL's are there
...elped. I am not sure what was wrong. I had a version of opencv, anaconda3, python3. Installed opencv_python-3.3.0+contrib-cp35-cp35m-win_amd64 from above package list and was able to import cv2 successfully after hours of struggle. Thanks a ton.
– emeralddove
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Shuffling a list of objects
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#!/usr/bin/python3
import random
s=list(range(5))
random.shuffle(s) # << shuffle before print or assignment
print(s)
# print: [2, 4, 1, 3, 0]
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How do I convert seconds to hours, minutes and seconds?
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@medley56 When using Python3, you need to use str() if you are going use a format such as 0>8: "{:0>8}".format(str(datetime.timedelta(seconds=666777))). Check this answer for more info.
– Berriel
Sep 1...