Reading Stdin with Multiple Datatypes

Question

Let's say you have input (command line arguments, txt file) that consists of multiple datatypes, like int and str. How can you efficiently turn each item into int if its a number, and str if its a str?

Example:

input.txt

A 1 B C 23 
5 D 0 E 2
143 E 6 A 1

output:

["A",1,"B","C",23]
[5,"D",0,"E",2]
[143,"E",6,"A",1]

Using open() and readlines(), you can store it in a variable and get:

['A 1 B C 23 \n', '5 D 0 E 2\n', '143 E 6 A 1']

But from here, if I want to use strip, I have to specify whether I want to convert everything to str() or int()- int() will cause error because it can't accept strings, and str() will just convert everything to string.

Answer 1

One option is to use exception handling:

import sys

def strint (s):
    try:
        x = int(s)
    except:
        x = s
    return x

for line in sys.stdin:
    print([strint(x) for x in line.split()])

With the above code in strint.py and the example input in the file strint.txt, we can run it to get the following output:

$ python strint.py <strint.txt
['A', 1, 'B', 'C', 23]
[5, 'D', 0, 'E', 2]
[143, 'E', 6, 'A', 1]

A more sophisticated version would catch the specific exceptions and could deal with floating point numbers, etc.