Difference between revisions of "CSC111 Exercises with Exceptions: try/except"
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</source> | </source> | ||
+ | <br /> | ||
+ | ==File Examples== | ||
+ | <br /> | ||
+ | ===Example 1=== | ||
+ | What could possibly go wrong with this code? | ||
+ | <source lang="python"> | ||
+ | def printUpperFile( fileName ): | ||
+ | file = open( fileName, "r" ) | ||
+ | for line in file: | ||
+ | print( line.upper() ) | ||
+ | file.close() | ||
+ | |||
+ | printUpperFile( "doesNotExistYest.txt" ) | ||
+ | printUpperFile( "./Dessssktop/misspelled.txt" ) | ||
+ | </source> | ||
+ | |||
<onlydft> | <onlydft> | ||
==Solution== | ==Solution== |
Revision as of 05:48, 2 April 2014
Code in need of try/except statements
- The program below is not very robust. We can easily make it crash.
- Observe each function and see how to make it fail, or see why it will fail the way it is called
- Make the program crash. Register the XXXXError that is generated. For example, if the output of the crash looks like this:
Traceback (most recent call last): File "/Users/thiebaut/Desktop/except0.py", line 29, in <module> main() File "/Users/thiebaut/Desktop/except0.py", line 27, in main example3( [ 10, 3, 5, 6 ] ) File "/Users/thiebaut/Desktop/except0.py", line 18, in example3 sum = sum + L[i] IndexError: list index out of range
- what you are interested in is IndexError. This is the exception you want to guard your code against.
try:
........
........
except IndexError:
.........
- Verify that you have made your functions more robust to erroneous input/data.
Code
def example1():
x = eval( input( "enter a number: " ) )
y = eval( input( "enter another number: " ) )
print( x, '/', y, '=', x/y )
def example2( L ):
print( "\n\nExample 2" )
sum = 0
for i in range( len( L ) ):
sum = sum + L[i]
print( "sum = ", sum )
def example3( L ):
print( "\n\nExample 3" )
sum = 0
for i in range( 6 ):
sum = sum + L[i]
print( "sum = ", sum )
def main():
example1()
L = [ 10, 3, 5, 6, 9, 3 ]
example2( L )
example2( [ 10, 3, 5, 6, "NA", 3 ] )
example3( [ 10, 3, 5, 6 ] )
main()
File Examples
Example 1
What could possibly go wrong with this code?
def printUpperFile( fileName ):
file = open( fileName, "r" )
for line in file:
print( line.upper() )
file.close()
printUpperFile( "doesNotExistYest.txt" )
printUpperFile( "./Dessssktop/misspelled.txt" )