Why this script can work?

[Jm lists]

Please help with this script:

class ShortInputException(Exception):
'''A user-defined exception class.'''
def __init__(self,length,atleast):
Exception.__init__(self)
self.length=length
self.atleast=atleast

try:
s=raw_input('Enter something --> ')
if len(s)<3:
raise ShortInputException(len(s),3)
# Other work can continue as usual here
except EOFError:
print '\nWhy did you do an EOF on me?'
except ShortInputException,x:
print 'ShortInputException: The input was of length %d, was
expecting at least %d' %(x.length,x.atleast)
else:
print 'No exception was raised.'


My questions are:

1) ShortInputException,x: what's the 'x'? where is it coming?

2) The 'if' and 'else' are not in the same indent scope,why this can work?

Thanks in advance.

 

[Diez B. Roggisch]

Please help with this script:

class ShortInputException(Exception):
'''A user-defined exception class.'''
def __init__(self,length,atleast):
Exception.__init__(self)
self.length=length
self.atleast=atleast

try:
s=raw_input('Enter something --> ')
if len(s)<3:
raise ShortInputException(len(s),3)
# Other work can continue as usual here
except EOFError:
print '\nWhy did you do an EOF on me?'
except ShortInputException,x:
print 'ShortInputException: The input was of length %d, was
expecting at least %d' %(x.length,x.atleast)
else:
print 'No exception was raised.'


My questions are:

1) ShortInputException,x: what's the 'x'? where is it coming?

except <ExceptionSpec>, <variable>:

will catch an exception of the kind specified in <ExceptionSpec> (it might
actually be more than one), and store the exception object in the variable

2) The 'if' and 'else' are not in the same indent scope,why this can work?

Because additionally to if, also for and try have else-clauses. The latter
two are only being called if the body of the control structure hasn't been
left due to "unnatural" circumstances. See this:




for i in xrange(10):
pass
else:
print "test 1"

for i in xrange(10):
break
else:
print "test 2"

try:
pass
except:
pass
else:
print "test 3"

try:
raise "I know I shouldn't rais strings..."
except:
pass
else:
print "test 4"



It will only print

test 1
test 3


Diez

 

[Jm lists]

Thanks for all the helps.
I'm not habitual for this usage of 'else',other languages seem don't
support this syntax.
i.g,writting the codes below by Perl would get an error:

# perl -le 'for $i (1..10){print $i} else{print "finished"}'
syntax error at -e line 1, near "}else"
Execution of -e aborted due to compilation errors.

 

[Diez B. Roggisch]

Thanks for all the helps.
I'm not habitual for this usage of 'else',other languages seem don't
support this syntax.
i.g,writting the codes below by Perl would get an error:

I personally consider this part of python also somewhat obscure. But I just
don't use it and don't bother.

Diez

 

[Gabriel Genellina]

I'm not habitual for this usage of 'else',other languages seem don't
support this syntax.
i.g,writting the codes below by Perl would get an error:

[[[censored example]]]

If all languages had the same features, what would be the point of having
different languages at all?