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Why does += behave unexpectedly on lists?
...print id(foo), id(f), id(g) (don't forget the additional ()s if you are on Python3).
BTW: The += operator is called "augmented assignment" and generally is intended to do inplace modifications as far as possible.
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How to form tuple column from two columns in Pandas
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in python3, you have to use list. This should work: df['new_col'] = list(zip(df.lat, df.long))
– paulwasit
Nov 2 '16 at 8:06
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Python group by
... the input to be sorted:
from functools import reduce # import needed for python3; builtin in python2
from collections import defaultdict
def groupBy(key, seq):
return reduce(lambda grp, val: grp[key(val)].append(val) or grp, seq, defaultdict(list))
(The reason for ... or grp in the lambda is t...
Create Pandas DataFrame from a string
...imple way to do this is to use StringIO.StringIO (python2) or io.StringIO (python3) and pass that to the pandas.read_csv function. E.g:
import sys
if sys.version_info[0] < 3:
from StringIO import StringIO
else:
from io import StringIO
import pandas as pd
TESTDATA = StringIO("""col1;co...
How do I raise the same Exception with a custom message in Python?
...g the extra information under your own variable name. For both python2 and python3:
try:
try:
raise ValueError
except ValueError as err:
err.extra_info = "hello"
raise
except ValueError as e:
print(" error was "+ str(type(e))+str(e))
if 'extra_info' in dir(e):
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What is the most compatible way to install python modules on a Mac?
...on25-apple
python26-apple
python27 (active)
python27-apple
python32
$ port select python python32
Add tox on top of it and your programs should be really portable
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Flattening a shallow list in Python [duplicate]
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@JosepVallsm nice solution! for python3 you need to use str instead of basestring, The builtin basestring abstract type was removed. Use str instead. The str and bytes types don’t have functionality enough in common to warrant a shared base class. The 2to...
Get exception description and stack trace which caused an exception, all as a string
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There is a simpler Python3 way without using .__traceback__ and type, see stackoverflow.com/a/58764987/5717886
– don_vanchos
Nov 8 '19 at 11:18
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Select random lines from a file
...s what I regularly use so that's what I'll use to make this faster:
#!/bin/python3
import random
f = open("lines_78000000000.txt", "rt")
count = 0
while 1:
buffer = f.read(65536)
if not buffer: break
count += buffer.count('\n')
for i in range(10):
f.readline(random.randint(1, count))
This...
How to re-raise an exception in nested try/except blocks?
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@user4815162342 Good point :) Though meanwhile in Python3 I'd consider raise from, so the stack trace would also let me se plan B failed. Which can be emulated in Python 2 by the way.
– Tobias Kienzler
Feb 4 '17 at 21:30
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