Reading a file line-by-line

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Example

The simplest way to iterate over a file line-by-line:

with open('myfile.txt', 'r') as fp:
    for line in fp:
        print(line)

readline() allows for more granular control over line-by-line iteration. The example below is equivalent to the one above:

with open('myfile.txt', 'r') as fp:
    while True:
        cur_line = fp.readline()
        # If the result is an empty string
        if cur_line == '':
            # We have reached the end of the file
            break
        print(cur_line)

Using the for loop iterator and readline() together is considered bad practice.

More commonly, the readlines() method is used to store an iterable collection of the file's lines:

with open("myfile.txt", "r") as fp:
    lines = fp.readlines()
for i in range(len(lines)):
    print("Line " + str(i) + ": " + line)

This would print the following:

Line 0: hello

Line 1: world

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Contributors: 5
2016-12-27
Licensed under: CC-BY-SA

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