count = len(open(fname,'r').readlines()) code example

Example 1: python how to count the lines in a file

# Basic syntax:
count = len(open('/path/to/the/file.ext').readlines())

Example 2: how to know how much lines a file has using python

filename = "test.txt"
count = 0
with open(filename, 'r') as f:
    for line in f:
        count += 1
print("Total number of lines is:", count)