I can't find imap() in itertools in Python 3
Question:
I have a problem that I want to solve with itertools.imap(). I imported itertools and called itertools.imap(), but apparently itertools doesn’t have attribute imap. What’s going wrong?
>>> import itertools
>>> dir(itertools)
['__doc__', '__loader__', '__name__', '__package__', '__spec__', '_grouper', '_tee', '_tee_dataobject', 'accumulate', 'chain', 'combinations', 'combinations_with_replacement', 'compress', 'count', 'cycle', 'dropwhile', 'filterfalse', 'groupby', 'islice', 'permutations', 'product', 'repeat', 'starmap', 'takewhile', 'tee', 'zip_longest']
>>> itertools.imap()
Traceback (most recent call last):
File "<pyshell#13>", line 1, in <module>
itertools.imap()
AttributeError: 'module' object has no attribute 'imap'
Answers:
You are using Python 3, therefore there is no imap function in itertools module. It was removed, because global function map now returns iterators.
itertools.imap() is in Python 2, but not in Python 3.
Actually, that function was moved to just the map function in Python 3 and if you want to use the old Python 2 map, you must use list(map()).
If you want something that works in both Python 3 and Python 2, you can do something like:
try:
from itertools import imap
except ImportError:
# Python 3...
imap=map
How about this?
imap = lambda *args, **kwargs: list(map(*args, **kwargs))
In fact!! 🙂
import itertools
itertools.imap = lambda *args, **kwargs: list(map(*args, **kwargs))
I like the python-future idoms for universal Python 2/3 code, like this:
# Works in both Python 2 and 3:
from builtins import map
You then have to refactor your code to use map everywhere you were using imap before:
myiter = map(func, myoldlist)
# `myiter` now has the correct type and is interchangeable with `imap`
assert isinstance(myiter, iter)
You do need to install future for this to work on both 2 and 3:
pip install future
You can use the 2to3 script (https://docs.python.org/2/library/2to3.html) which is part of every Python installation to translate your program or whole projects from Python 2 to Python 3.
python <path_to_python_installation>Toolsscripts2to3.py -w <your_file>.py
(-w option writes modifications to file, a backup is stored)
I have a problem that I want to solve with itertools.imap(). I imported itertools and called itertools.imap(), but apparently itertools doesn’t have attribute imap. What’s going wrong?
>>> import itertools
>>> dir(itertools)
['__doc__', '__loader__', '__name__', '__package__', '__spec__', '_grouper', '_tee', '_tee_dataobject', 'accumulate', 'chain', 'combinations', 'combinations_with_replacement', 'compress', 'count', 'cycle', 'dropwhile', 'filterfalse', 'groupby', 'islice', 'permutations', 'product', 'repeat', 'starmap', 'takewhile', 'tee', 'zip_longest']
>>> itertools.imap()
Traceback (most recent call last):
File "<pyshell#13>", line 1, in <module>
itertools.imap()
AttributeError: 'module' object has no attribute 'imap'
You are using Python 3, therefore there is no imap function in itertools module. It was removed, because global function map now returns iterators.
itertools.imap() is in Python 2, but not in Python 3.
Actually, that function was moved to just the map function in Python 3 and if you want to use the old Python 2 map, you must use list(map()).
If you want something that works in both Python 3 and Python 2, you can do something like:
try:
from itertools import imap
except ImportError:
# Python 3...
imap=map
How about this?
imap = lambda *args, **kwargs: list(map(*args, **kwargs))
In fact!! 🙂
import itertools
itertools.imap = lambda *args, **kwargs: list(map(*args, **kwargs))
I like the python-future idoms for universal Python 2/3 code, like this:
# Works in both Python 2 and 3:
from builtins import map
You then have to refactor your code to use map everywhere you were using imap before:
myiter = map(func, myoldlist)
# `myiter` now has the correct type and is interchangeable with `imap`
assert isinstance(myiter, iter)
You do need to install future for this to work on both 2 and 3:
pip install future
You can use the 2to3 script (https://docs.python.org/2/library/2to3.html) which is part of every Python installation to translate your program or whole projects from Python 2 to Python 3.
python <path_to_python_installation>Toolsscripts2to3.py -w <your_file>.py
(-w option writes modifications to file, a backup is stored)