How to test if every item in a list of type 'int'?

Question

Say I have a list of numbers. How would I do to check that every item in the list is an int?
I have searched around, but haven\'t been able to find anything on this.

Answer 1

The following statement should work. It uses the any builtin and a generator expression:

any(not isinstance(x, int) for x in l)

This will return true if there is a non-int in the list. E.g.:

>>> any(not isinstance(x, int) for x in [0,12.])
True
>>> any(not isinstance(x, int) for x in [0,12])
False

The all builtin could also accomplish the same task, and some might argue it is makes slightly more sense (see Dragan's answer)

all(isinstance(x,int) for x in l)

Answer 2

Found myself with the same question but under a different situation: If the "integers" in your list are represented as strings (e.g., as was the case for me after using 'line.split()' on a line of integers and strings while reading in a text file), and you simply want to check if the elements of the list can be represented as integers, you can use:

all(i.isdigit() for i in myList)

For example:

>>> myList=['1', '2', '3', '150', '500', '6']
>>> all(i.isdigit() for i in myList)
True

>>> myList2=['1.5', '2', '3', '150', '500', '6']
>>> all(i.isdigit() for i in myList2)
False

Answer 3

lst = [1,2,3]
lst2 = [1,2,'3']

list_is_int = lambda lst: [item for item in lst if isinstance(item, int)] == lst

print list_is_int(lst)
print list_is_int(lst2)

suxmac2:~$ python2.6 xx.py 
True
False

....one possible solution out of many using a list comprehension or filter()

Answer 4

>>> my_list = [1, 2, 3.25]
>>> all(isinstance(item, int) for item in my_list)
False

>>> other_list = range(3)
>>> all(isinstance(item, int) for item in other_list)
True
>>> 

Answer 5

See functions

def is_int(x):
    if type(x) == int:
        return True
    return


def all_int(a):
    for i in a:
        if not is_int(i):
            return False
    return True

Then call

all_int(my_list) # returns boolean

Answer 6

In [1]: a = [1,2,3]

In [2]: all(type(item)==int for item in a)
Out[2]: True