Python for Entrepreneurs Transcripts
Chapter: Appendix: Python language concepts
Lecture: Concept: File I/O
0:01 Working with files in Python, especially text files
0:03 is something that you are likely to need in your application.
0:06 So let's take a really simple example.
0:09 Here we are going to create a file,
0:11 we have three items in our data structure we want to save on the three separate lines,
0:15 so we have cat, hat, mat and a list, and these are just strings.
0:18 We are going to use the "open" method,
0:20 and the "open" method takes a file name and a modifier,
0:23 and then this "open" method, the open string that comes back
0:26 can be used as a context manager, so we are putting into a "with" block,
0:30 and naming the variable fout for file output,
0:33 and this automatically closes the file stream, as soon as we leave this with block.
0:38 So that's really nice and safe, makes sure we flush, it close it, all those kinds of things.
0:42 Once we get the file open, we are going to loop over each item
0:45 and we are just going to say "fout.write" and pass it the item, so cat, hat or mat.
0:50 Now, write does not append a new line, it just writes characters to the file,
0:54 so we want to say "\n" to append a new line,
0:57 so each one of these items up here is on a separate line in the file.
1:01 And notice this "w" modifier, this means write only and truncate the file if it exists.
1:06 We could also say "a" for append, "a+" for create an append
1:11 or "r" if we just wanted to read from the file but not write to it.
1:15 There is also a "b" modifier for binary files, but you'll use that less often.