[Tutor] Recognizing real numbers

[Joel Goldstick]

On Wed, Feb 22, 2012 at 4:35 PM, bob gailer <bgailer at gmail.com> wrote:
> On 2/21/2012 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?
>
> Wow - the requirements just changed. Up tilll now we were dealing with
> multiplying each digit. Now we have to parse out a string that represents a
> number with decimal places! I hope that we don't raise the oven temperature
> in the process.
>
> Is it true that the number to multiply is always at the beginning of a line?
> If so that makes the job a lot easier.
>
> 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)
>
> Module doing the importing/opening/reading/creating a new file
>
> import Homework5_1 as multiply
>
> def DoubleDigits(file_name):
>     '''Open file/read file/write new file that doubles all int's in the
>     read file'''
>     try:
>         read_file = open(file_name)
>     except IOError:
>         return 'No such file.'
>     new_file_name = file_name + '2'
>     try:
>         write_file = open(new_file_name, 'w')
>     except IOError:
>         read_file.close()
>         return 'No such file to write to.'
>     for line in read_file:
>         new_line = line.split()
>         new_line = ''.join(multiply.MultiplyText(new_line, 2))
>         write_file.write(new_line + '\n')
>     read_file.close()
>     write_file.close()
>
> def main():
>     DoubleDigits(raw_input('What file do you want to open? '))
>
>
> if '__name__' == '__main__':
>     print main()
>
> Output that is written to my file:
>
> Peanut Butter Bars
>
> Ingredients
>
> .5 lb. butter
> 1.75 Cups Graham Cracker Crumbs
> 4.0 Cups Powder Sugar
> 2.0 Cups Peanut Butter
> 4.0 Cups Semi-sweet Chocolate Chips
>
> Melt butter. Add graham cracker crumbs,
> peanut butter and sugar. Mix well and
> pat into sheet pan. Cover with melted
> chocolate. Refrigerate until semi-firm,
> then cut into squares.
>
> --
> Michael J. Lewis
>
>
>
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>
>
> --
> Bob Gailer
> 919-636-4239
> Chapel Hill NC
>
>
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>
If the first stuff in the line is always the number, and you capture
the line in s then:

n  = float(s.split()[0])   will give you the number.  You should wrap
this up with a try block so that it doesn't fail if it isn't a number

split method separates on whitespace and puts each part of the string
in a list.  [0] takes the first of those list items.  float converts
to a float




-- 
Joel Goldstick