Python for Entrepreneurs Transcripts
Chapter: Appendix: Python language concepts
Lecture: Concept: File I/O
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0:01
Working with files in Python, especially text files
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is something that you are likely to need in your application.
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So let's take a really simple example.
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Here we are going to create a file,
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we have three items in our data structure we want to save on the three separate lines,
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so we have cat, hat, mat and a list, and these are just strings.
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We are going to use the "open" method,
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and the "open" method takes a file name and a modifier,
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and then this "open" method, the open string that comes back
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can be used as a context manager, so we are putting into a "with" block,
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and naming the variable fout for file output,
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and this automatically closes the file stream, as soon as we leave this with block.
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So that's really nice and safe, makes sure we flush, it close it, all those kinds of things.
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Once we get the file open, we are going to loop over each item
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and we are just going to say "fout.write" and pass it the item, so cat, hat or mat.
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Now, write does not append a new line, it just writes characters to the file,
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so we want to say "\n" to append a new line,
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so each one of these items up here is on a separate line in the file.
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And notice this "w" modifier, this means write only and truncate the file if it exists.
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We could also say "a" for append, "a+" for create an append
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or "r" if we just wanted to read from the file but not write to it.
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There is also a "b" modifier for binary files, but you'll use that less often.
