Question

a = raw_input('How much is 1 share in that company? ')

while not a.isdigit():
    print("You need to write a number!\n")
    a = raw_input('How much is 1 share in that company? ')

This only works if the user enters an integer, but I want it to work even if they enter a float, but not when they enter a string.

So the user should be able to enter both 9 and 9.2, but not abc.

How should I do it?

Answer 1

Use regular expressions.

import re

p = re.compile('\d+(\.\d+)?')

a = raw_input('How much is 1 share in that company? ')

while p.match(a) == None:
    print "You need to write a number!\n"
    a = raw_input('How much is 1 share in that company? ')