Python "int object not iterable" after list() a map object

Question

The following simple code returns an error, even with list():

map(max,[1,2,3,4])
Out[123]: <map at 0xdff50f0320>
list(map(max,[1,2,3,4]))
TypeError: 'int' object is not iterable

I used list to map object is to display the content; it seems not work this way. How to see the map object?

map(max, [1,2,3,4]) calls max(1), then max(2), then max(3), then max(4). None of those calls make any sense. What did you want it to call? Just max([1,2,3,4]) without map? Or something different? — abarnert
– abarnert, Commented Aug 22, 2018 at 0:02
The reason you don't get an error from just map(max, [1,2,3,4]) without the list(…) is that you're just creating the map iterator. It doesn't try to call map(1) (which raises the exception) until you try to use the iterator. — abarnert
– abarnert, Commented Aug 22, 2018 at 0:03

Prune · Accepted Answer · 2018-08-22 00:04:50Z

1

map applies the given function to each element of the iterable object that follows. What you've tried to do is to take the maximum of four integers, individually. Since max also requires an iterable object, this fails.

Usage example:

l = [
      [1, 2, 3, 4],
      [3.14, 2.7, 6.023, -5],
      ['Python', 'Java', 'R']
    ]

large = map(max, l)
for big in large:
    print (big)

Output:

4
6.023
R

answered Aug 22, 2018 at 0:04

Prune

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1 Comment

user3078106 Over a year ago

great. Thanks for pointing out max() is done individually. Also appreciate the point from the other comment why there's no error in map(). By the way, the example didn't mean to have any meaningful usage. Just highlight the error.

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