[Tutor] New to this list ....

[Prasad, Ramit]

> > Hi there ....  I've just joined this list and thought I'd introduce 
myself.  

Welcome!

> > correct = 0
> >     match = 0
> >     wrong = 0
> >     results = [correct, match, wrong]
> >
> >     results = getflag(flag_1, results)
> >     results = getflag(flag_2, results)
> >     results = getflag(flag_3, results)
> >     results = getflag(flag_4, results)

>> def getflag(thisflag, results):
>>      if (thisflag == 2):
>>          results[0] += 1
>>      elif (thisflag == 1):
>>          results[1] += 1
>>      elif (thisflag == 0):
>>          results[2] += 1
>>      return(results)
>> 
>> In c, I would have used switch and case, but I gather there is no direct
>> equivalent in Python ...   But it works as is.

C switch is just a different way of doing an if/elif tree, I do not 
really see any real difference. Although, if there is you can feel free 
to enlighten me. :)

Unlike C, the parenthesis in if statements and returns are not necessary.

>      if (thisflag == 2):
becomes
      if thisflag == 2:

>      return(results)
becomes 
      return results

Furthermore, the way Python binds names means that modifying the list
in getflags modifies it in the callee. No need to return and reassign 
results.

>>> def foo(x):
...     x[0] += 1
...     
>>> bar = [ 1, 3, 4 ]
>>> foo( bar )
>>> print bar
[2, 3, 4]
>>> foo( bar )
>>> print bar
[3, 3, 4]

Be careful of "results = [0] * 3". This style works fine for immutable
types (int, float, str) but does not work as people new to Python think
it does. 

>>> def foo(x):
...     x[0][0] += 1
...     
>>> bar = [ [0] ]*3
>>> print bar
[[0], [0], [0]]
>>> foo( bar )
>>> print bar
[[1], [1], [1]]
>>> foo( bar )
>>> print bar
[[2], [2], [2]]

This occurs because bar is a list containing 3 elements which are 
all the exact same object. Modifying one sub-list will modify the
"others" as well. 

Ramit


Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology
712 Main Street | Houston, TX 77002
work phone: 713 - 216 - 5423

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