1.8. The Interactive Shell
Now that you have Python installed, what's this interactive shell thing you're running?
It's like this: Python leads a double life. It's an interpreter for scripts that you can run from the command line or run like applications, by
double-clicking the scripts. But it's also an interactive shell that can evaluate arbitrary statements and expressions.
This is extremely useful for debugging, quick hacking, and testing. I even know some people who use the Python interactive shell in lieu of a calculator!
Launch the Python interactive shell in whatever way works on your platform, and let's dive in with the steps shown here:
Example 1.5. First Steps in the Interactive Shell
>>> 1 + 1 
2
>>> print 'hello world' 
hello world
>>> x = 1 
>>> y = 2
>>> x + y
3
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The Python interactive shell can evaluate arbitrary Python expressions, including any basic arithmetic expression.
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The interactive shell can execute arbitrary Python statements, including the print statement.
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You can also assign values to variables, and the values will be remembered as long as the shell is open (but not any longer
than that).
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