I'm guessing that you need to assign the Exception to a variable. As shown in the Python 3 tutorial:
def fails():
x = 1 / 0
try:
fails()
except Exception as ex:
print(ex)
To give a brief explanation, as is a pseudo-assignment keyword used in certain compound statements to assign or alias the preceding statement to a variable.
In this case, as assigns the caught exception to a variable allowing for information about the exception to stored and used later, instead of needing to be dealt with immediately. (This is discussed in detail in the Python 3 Language Reference: The try Statement.)
The other compound statement using as is the with statement:
@contextmanager
def opening(filename):
f = open(filename)
try:
yield f
finally:
f.close()
with opening(filename) as f:
# ...read data from f...
Here, with statements are used to wrap the execution of a block with methods defined by context managers. This functions like an extended try...except...finally statement in a neat generator package, and the as statement assigns the generator-produced result from the context manager to a variable for extended use.
(This is discussed in detail in the Python 3 Language Reference: The with Statement.)
Finally, as can be used when importing modules, to alias a module to a different (usually shorter) name:
import foo.bar.baz as fbb
This is discussed in detail in the Python 3 Language Reference: The import Statement.