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Replacing instances of a character in a string
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Strings in python are immutable, so you cannot treat them as a list and assign to indices.
Use .replace() instead:
line = line.replace(';', ':')
If you need to replace only certain semicolons, you'll need to be more specific. You co...
How To Check If A Key in **kwargs Exists?
Python 3.2.3. There were some ideas listed here , which work on regular var's, but it seems **kwargs play by different rules... so why doesn't this work and how can I check to see if a key in **kwargs exists?
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how does multiplication differ for NumPy Matrix vs Array classes?
...ally I find it more trouble than it's worth, though.
For arrays (prior to Python 3.5), use dot instead of matrixmultiply.
E.g.
import numpy as np
x = np.arange(9).reshape((3,3))
y = np.arange(3)
print np.dot(x,y)
Or in newer versions of numpy, simply use x.dot(y)
Personally, I find it much mo...
What does functools.wraps do?
...otation on the values copied over. Fundamentally, it's an extension of the Python philosophy that explicit is better than implicit and special cases aren't special enough to break the rules. (The code is much simpler and the language easier to understand if @wraps must be provided manually, rather t...
Regex doesn't work in String.matches()
...ly C++ has an equivalent set of methods - regex_search and regex_match. In Python, re.match only anchors the match at the start of the string (as if it were \Apattern) and Python 3.x has got a nice .fullmatch() method. In JS, Go, PHP and .NET, the there are no regex methods that anchor the match imp...
How to raise a ValueError?
... name for this function. Adding to the possible confusion is the fact that Python already has a container object method named __contains__() that does something a little different, membership-testing-wise.
def contains(char_string, char):
largest_index = -1
for i, ch in enumerate(char_strin...
How can I check the extension of a file?
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Use pathlib From Python3.4 onwards.
from pathlib import Path
Path('my_file.mp3').suffix == '.mp3'
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When to use pip requirements file versus install_requires in setup.py?
I'm using pip with virtualenv to package and install some Python libraries.
4 Answers
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Converting Epoch time into the datetime
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see docs.python.org/2/library/time.html#time.strftime for more info in the format string
– georg
Jul 27 '13 at 21:01
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Algorithm to return all combinations of k elements from n
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May I present my recursive Python solution to this problem?
def choose_iter(elements, length):
for i in xrange(len(elements)):
if length == 1:
yield (elements[i],)
else:
for next in choose_iter(elements[i+1...