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files and exceptions

Try first, then recover

Rather than adding extra code and logic to guard against bad things
happening, Python’s exception handling mechanism lets the error occur,
spots that it has happened, and then gives you an opportunity to recover.
During the normal flow of control, Python tries your code and, if nothing goes
wrong, your code continues as normal. During the exceptional flow of control,
Python tries your code only to have something go wrong, your recovery code
executes, and then your code continues as normal.
Exceptional flow
Python tries
Normal flow your code, but
fails!

Python tries
your code.
Crash!
Your recovery
code executes.
Your exception
It’s all OK, so is handled.
keep going…

The try/except mechanism Then you keep
going…
Python includes the try statement, which exists to provide you with a way to
systematically handle exceptions and errors at runtime. The general form of
the try statement looks like this:
try:

Both “try”
and “except” your code (which might cause a runtime error)
are Python
keywords.
except:

your error-recovery code

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