TypeError: 'in <string>' requires a string as a left operand, not an int

Question

Why am I getting this error in the most basic Python script? What does the error mean?

Error:

Traceback (most recent call last):
  File "cab.py", line 16, in <module>
    if cab in line:
TypeError: 'in <string>' requires string as left operand, not int

Script:

import re
import sys

#loco = sys.argv[1]
cab = 6176
fileZ = open('cabs.txt')
fileZ = list(set(fileZ))

for line in fileZ:
     if cab in line: 
        IPaddr = (line.strip().split())
        print(IPaddr[4])

Answer 1

You just need to make a cabline:

cab = '6176'

As indicated in the error message, you cannot do <int> in <string>:

>>> 1 in '123'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'in <string>' requires string as left operand, not int
>>> 

because integers and strings are two completely different things and Python doesn't use an implicit type conversion ( Explicit is better than implicit. ).

In fact, Python allows you to use an operator inwith the correct operand of a type string if the left operand also has a type string:

>>> '1' in '123'  # Works!
True
>>>
>>> [] in '123'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'in <string>' requires string as left operand, not list
>>>
>>> 1.0 in '123'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'in <string>' requires string as left operand, not float
>>>
>>> {} in '123'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'in <string>' requires string as left operand, not dict
>>>