Examples of how to check if a python variable is a number (integer, float):

### Check if a python variable is a number using isinstance

To check if a python variable is a number (int or float par example), a solution is to use isinstance:

`x = 1.2`

`isinstance(x, (int, float))`

returns here

`True`

while

`x = 'abcd'`

`isinstance(x, (int, float))`

returns

` false`

### Case of a string variable

In the case of a string variable

`x = '1'`

the function isinstance

`isinstance(x, (int, float))`

will return

`False`

but to test if a string represents a number, a solution is to use isdigit, example

`x = '1'`

`x.isdigit()`

returns

`True`

### Filter a list to keep only numbers

Example of application, let's consider the following list:

`l = [5, 3, 2, 'a', 9, 1, 4, 'NaN']`

that can be filtered to keep only the numbers

que l'on peut filtrer pour ne garder que les nombres:

`l = [i for i in l if isinstance(i, (int, float))]`

`print(l)`

returns

`[5, 3, 2, 9, 1, 4]`