I am trying to import the izip module like so:
from itertools import izip
However after recently changing over from Python 2.7 to 3 - it doesn't seem to work.
I am trying to write to a csv file:
writer.writerows(izip(variable1,2))
But I have no luck. Still encounter an error.
izip() returns an iterator that combines the elements of the passed iterators into tuples. It works similarly to zip() , but returns an iterator instead of a list.
Itertools is a module in Python, it is used to iterate over data structures that can be stepped over using a for-loop. Such data structures are also known as iterables. This module works as a fast, memory-efficient tool that is used either by themselves or in combination to form iterator algebra.
The itertools. combinations() function takes two arguments—an iterable inputs and a positive integer n —and produces an iterator over tuples of all combinations of n elements in inputs . >>> list(it. combinations(bills, 3)) [(20, 20, 20), (20, 20, 10), (20, 20, 10), ... ]
In Python 3 the built-in zip
does the same job as itertools.izip
in 2.X(returns an iterator instead of a list). The zip
implementation is almost completely copy-pasted from the old izip
, just with a few names changed and pickle support added.
Here is a benchmark between zip
in Python 2 and 3 and izip
in Python 2:
Python 2.7:
from timeit import timeit print(timeit('list(izip(xrange(100), xrange(100)))', 'from itertools import izip', number=500000)) print(timeit('zip(xrange(100), xrange(100))', number=500000))
Output:
1.9288790226 1.2828938961
Python 3:
from timeit import timeit print(timeit('list(zip(range(100), range(100)))', number=500000))
Output:
1.7653984297066927
In this case since zip
's arguments must support iteration you can not use 2 as its argument. So if you want to write 2 variable as a CSV row you can put them in a tuple or list:
writer.writerows((variable1,2))
Also from itertools
you can import zip_longest
as a more flexible function which you can use it on iterators with different size.
One of the ways which helped me is:
try: from itertools import izip as zip except ImportError: # will be 3.x series pass
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