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Engineering LibreTexts

14.2: Reading and writing

  • Page ID
    40809
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    A text file is a sequence of characters stored on a permanent medium like a hard drive, flash memory, or CD-ROM. We saw how to open and read a file in Section 9.1.

    To write a file, you have to open it with mode 'w' as a second parameter:

    >>> fout = open('output.txt', 'w')
    

    If the file already exists, opening it in write mode clears out the old data and starts fresh, so be careful! If the file doesn’t exist, a new one is created.

    open returns a file object that provides methods for working with the file. The write method puts data into the file.

    >>> line1 = "This here's the wattle,\n"
    >>> fout.write(line1)
    24
    

    The return value is the number of characters that were written. The file object keeps track of where it is, so if you call write again, it adds the new data to the end of the file.

    >>> line2 = "the emblem of our land.\n"
    >>> fout.write(line2)
    24
    

    When you are done writing, you should close the file.

    >>> fout.close()
    

    If you don’t close the file, it gets closed for you when the program ends.


    This page titled 14.2: Reading and writing is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Allen B. Downey (Green Tea Press) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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