pythoninput

Input always eats one character

A need multiline input in Python (I have v3.12.3) and I want to end the stream by pressing Ctrl+D But it always eats one character at the end.

def main():
    lines = []
    while True:
        try:
            line = input()
            lines.append(line)
        except EOFError:
            break
    print(lines)
    
if __name__=="__main__":
    main()

If I run the program and type 3 times '-' and then press Ctrl+D I got only 2 '-' Similarly 'abc' results in 'ab'.

What am I doing wrong? I need all the data that the user inputs.

Solution

  • Use sys.stdin.read() instead of input()

    The issue is that when input() function processes the EOF (Ctrl+D) it terminates the current line without processing the final character entered before it.

    Use sys.stdin.read() instead.

    import sys

def main():
    try:
        lines = sys.stdin.read().splitlines()
        print(lines)
    except EOFError:
        pass

if __name__ == "__main__":
    main()

    Why does this happen? Explanation:

    The input() function reads input line-by-line, stopping at a newline (\n). If EOF (e.g., Ctrl+D on Unix/macOS, Ctrl+Z + Enter on Windows) is sent before a newline, input() won't process the final incomplete line because it expects a newline to complete the input.

    On the other hand, sys.stdin.read() reads the entire input stream until EOF, including any partial lines before the EOF signal. This is because it treats input as a continuous stream rather than discrete lines.

    Key Difference: