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Python has some very simple built- in functions for dealing with files.

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Let's make a working copy of files.py.

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I'll call it files-working.py and we will open that working file and we see here

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a simple loop that reads lines from a file and prints them out.

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So run that and see what it does.

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It prints out the lines of this file. This is the file here, lines.txt, and we

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are just printing out all five lines with that file in this little loop.

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What we are going to look at in this movie is this open function.

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It's very simple and it has a few options.

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By default, all it does is it opens the files in the read mode and you give it a

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file name here and it returns the file handle object, which can then be used to

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operate on the file.

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If you don't specify it, read mode is the default and that looks like this.

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There is the second argument, which is the mode, and that defaults to the

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r character for read.

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Options there are r for read, w for write, or a for append.

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Append is a special write mode.

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It sets the current position of the file to the end of the file so that

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everything that you write will get appended to the file.

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In read mode, you can optionally give it a plus sign, which will open it for both

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read and write in the same file handle object.

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You can also give it a t for text file mode or a b for binary mode, and we will

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look at these options a little later in our movie on the subject.

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The open function returns this file handle object, which we see used here.

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It is an iterable object and in iteration mode it simply gives you one line

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of the file at a time.

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In fact, there is a method called read lines, which does exactly the same thing.

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You save that and run it, and there is our lines of text.

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So that is the open function in all of its simplicity.

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In the rest of this chapter we will look at how to read and write files and how

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to set its file mode.