How Can I Efficiently Remove Newlines from File Data Read with Python's `readlines()`?

Stripping Newlines from File Data in Python

When reading a file in Python using the readlines() method, the resulting list elements contain newlines at the end. To eliminate these newlines, several approaches are available.

One method is to utilize string's splitlines() function to split lines on newlines after reading the entire file:

temp = file.read().splitlines()

Alternatively, you can manually strip the newlines:

temp = [line[:-1] for line in file]

Note: This method assumes the file ends with a newline; otherwise, the last line will be truncated.

To ensure the presence of an ending newline, you can add one manually:

with open(the_file, 'r+') as f:
    f.seek(-1, 2)
    if f.read(1) != '\n':
        f.write('\n')
        f.flush()
        f.seek(0)
    lines = [line[:-1] for line in f]

Another option is to use strip() to remove newlines:

[line.rstrip('\n') for line in file]

For conciseness, you can also employ the below approach:

[line[:-(line[-1] == '\n') or len(line)+1] for line in file]

Understanding readlines()

The readlines() method iterates over readline(), which includes newlines. Thus, so does readlines(). For consistency, writelines() does not add newlines, ensuring an exact copy is produced when using both methods.

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