Open and iterate over file Python

Create a file handler with the builtin open():

file = open("input.txt", "r", encoding="utf-8")

...

# Ensure you close the file when you're done!
file.close()

It's recommended to use a with block when dealing with files, which automatically closes the file when the scope finished:

with open("input.txt", encoding="utf-8") as input:
    # You can then iterate over the lines, since the file also acts as an iterator
    for line in input:
        print(line)

See Input and Output - Python documentation