[Tutor] Recognizing real numbers
d at davea.name
Wed Feb 22 23:52:37 CET 2012
On 02/21/2012 10:00 PM, Michael Lewis wrote:
> Hi everyone,
> I have some code where I import a file to use a module. That module that I
> import takes text and a multiplier, checks for any numbers in that text and
> will then multiply those numbers by the given multiplier. The imported
> module is below. I am getting the text from a file that I have which starts
> out as:
> .5 lb. butter
> 1.75 Cups Graham Cracker Crumbs
> 2.0 Cups Powder Sugar
> 1.0 Cups Peanut Butter
> 2.0 Cups Semi-sweet Chocolate Chips
> It seems that the .isdigit() function that I use doesn't recognize the .5
> as a number and therefore doesn't multiply it. How can I get my code to
> recognize numbers such as .5, 1.75 as numbers?
> Imported module:
> def MultiplyText(text, multiplier):
> '''Recieve a S& int. For digits in S, multiply by multiplier and
> return updated S.'''
> return ' '.join(str(float(num) * multiplier) if num.isdigit() else num
> for num in text)
Somehow, every other time I read that code I missed the "for num in
text" phrase that was wrapped around by the mail.
I'm apologizing for my earlier remarks stating that this function would
not work. i would clean up the variable names (text is a list, and num
is a string), and the function comment states that you're multiplying
individual digits). But since it works, it's a good base to start with
for your floating point question.
Easiest answer is to write a function that does check if a string is a
valid float, the same as num.isdigit() (lousy names also occur in the
standard library) does for int.
The new function would be easiest to write with a try/except form. Take
a string as a formal parameter, try to float() it in a try block, and if
it succeeds, return True.
It'd be convenient if there were such a method in str, but since there
isn't, you'd have to change num.isdigit() to isfloat(num).
Have you gotten to try/except in your class yet?
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