Python: Journey from Novice to Expert by Fabrizio Romano

Author:Fabrizio Romano
Language: eng
Format: epub
Publisher: Packt Publishing

File I/O

Our examples so far that touch the filesystem have operated entirely on text files without much thought to what is going on under the hood. Operating systems, however, actually represent files as a sequence of bytes, not text. We'll do a deep dive into the relationship between bytes and text in Chapter 8, Strings and Serialization. For now, be aware that reading textual data from a file is a fairly involved process. Python, especially Python 3, takes care of most of this work for us behind the scenes. Aren't we lucky?

The concept of files has been around since long before anyone coined the term object-oriented programming. However, Python has wrapped the interface that operating systems provide in a sweet abstraction that allows us to work with file (or file-like, vis-á-vis duck typing) objects.

The open() built-in function is used to open a file and return a file object. For reading text from a file, we only need to pass the name of the file into the function. The file will be opened for reading, and the bytes will be converted to text using the platform default encoding.

Of course, we don't always want to read files; often we want to write data to them! To open a file for writing, we need to pass a mode argument as the second positional argument, with a value of "w":

contents = "Some file contents" file = open("filename", "w") file.write(contents) file.close()

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