[Tutor] parsing a blank-separated string into a list

[Simon Brunning]

> From:	Eugene Leitl [SMTP:Eugene.Leitl@lrz.uni-muenchen.de]
> Assuming, I have a string like this (produced by the JME applet,
> encoding a molecule I entered):
> 
> 10 11 C 9.13 -8.85 C 10.34 -8.15 C 7.92 -8.15 C 10.34 -6.75 C 7.92 -6.75 C
> 8.43 -3.89 C 9.83 -3.89 C 8.00 -5.23 C 10.26 -5.23 C+ 9.13 -6.05 1 2 2 1 3
> 1 2 4 1 3 5 2 4 10 2 5 10 1 6 7 1 6 8 1 7 9 1 8 10 1 9 10 1
> 
> And want to turn it into a list like this:
> 
> [10, 11, C, 9.13 ... ]
> 
> How do I do it?
> 
> jmelist = map(None, jmevalue) produces
> 
> [1, 0, 1, 1, C, ...], whereas I want the blank-separted atoms.
 
Try this

mystring = '''10 11 C 9.13 -8.85 C 10.34 -8.15 C 7.92 -8.15 C 10.34 -6.75 C
7.92 -6.75 C 8.43 -3.89 C 9.83 -3.89 C 8.00 -5.23 C 10.26 -5.23 C+ 9.13
-6.05 1 2 2 1 3 1 2 4 1 3 5 2 4 10 2 5 10 1 6 7 1 6 8 1 7 9 1 8 10 1 9 10
1'''
mylist = mystring.split()

At this point, mylist consists of a list of strings. It looks like you want
the numeric strings converted into numbers. Floats by the look of it. Now,
if your strings were *all* numeric, you could do:

mylist = [float(value) for value in mylist]

and you would be fine. List comprehensions are nice. ;-)

But in your case, this would blow up with a ValueError when trying to
convert the alphabetic characters, so we'll have to do this the old
fashioned way:

for index in range(len(mylist)):
    try:
        mylist[index] = float(mylist[index])
    except ValueError:
        pass

BTW, if you are not familiar with floats, you have a lot of surprises coming
up. If you are, then you *still* have a lot of surprises coming up. ;-)

HTH,
Simon B.




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