Is there a way to output the numbers only from a python list?

Question

Simple Question:

list_1 = [ 'asdada', 1, 123131.131, 'blaa adaraerada', 0.000001, 34.12451235265, 'stackoverflow is awesome' ]

I want to create a list_2 such that it only contains the numbers:

list_2 = [ 1, 123131.131, 0.000001, 34.12451235265 ]

Is there simplistic way of doing this, or do I have to resort to checking the variable type of each list item and only output the numerical ones?

Answer 1

列出理解。

list_2 = [num for num in list_1 if isinstance(num, (int,float))]

Answer 2

This should be the most efficient and shortest in Python 2:

import operator
filter(operator.isNumberType, list_1)

This in Python 3:

import numbers
[x for x in list_1 if isinstance(x, numbers.Number)]

Answer 3

list_2 = [i for i in list_1 if isinstance(i, (int, float))]

Answer 4

All solutions proposed work only if the numbers inside the list are already converted to the appropriate type ( int , float ).

I found myself with a list coming from the fetchall function of sqlite3 . All elements there were formated as str , even if some of those elements were actually integers.

cur.execute('SELECT column1 FROM table1 WHERE column2 = ?', (some_condition, ))
list_of_tuples = cur.fetchall()

The equivalent from the question would be having something like:

list_1 = [ 'asdada', '1', '123131', 'blaa adaraerada', '0', '34', 'stackoverflow is awesome' ]

For such a case, in order to get a list with the integers only, this is the alternative I found:

list_of_numbers = []
for tup in list_of_tuples:
    try:
        list_of_numbers.append(int(tup[0]))
    except ValueError:
        pass

list_of_numbers will contain only all integers from the initial list.

Answer 5

I think the easiest way is:

[s for s in myList if s.isdigit()]

Hope it helps!

Answer 6

filter(lambda n: isinstance(n, int), [1,2,"three"])

Answer 7

list_2 = [i for i in list_1 if isinstance(i, (int, float))]

Answer 8

>>> [ i for i in list_1 if not str(i).replace(" ","").isalpha() ]
[1, 123131.13099999999, 9.9999999999999995e-07, 34.124512352650001]

Answer 9

for short of SilentGhost way

list_2 = [i for i in list_1 if isinstance(i, (int, float))] 

to

list_2 = [i for i in list_1 if not isinstance(i, str)]

Answer 10

list_1 = [ 'asdada', 1, 123131.131, 'blaa adaraerada', 0.000001, 34.12451235265, 'stackoverflow is awesome' ]

first example:

list_2 = [x for x in list_1 if type(x) == int or type(x) == float ]
print(list_2)

second example:

list_2 = [x for x in list_1 if isinstance(x, (int, float)) ]
print(list_2)