Outputting a line that starts with...?

Question

Python

Hello! I have a text document that I have already opened and read with Python, now I want to count the number of lines that start with 123(text) for example. That is, they start with 123 and what is in brackets no longer matters.

Answer 1

with open('file', 'r') as fp:
  print len([i for i in fp if i.startswith('123')])

Answer 2

as an option, you translate its contents into str and compare with the first three characters 123

if mystr[0:3] == '123':
    condition1
else:
    condition2