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From: Peter Otten <__peter__@web.de>
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Subject: Re: Simple exercise
Date: Thu, 10 Mar 2016 10:41:34 +0100
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Xref: csiph.com comp.lang.python:104497

Rodrick Brown wrote:

> From the following input
> 
> 9
> BANANA FRIES 12
> POTATO CHIPS 30
> APPLE JUICE 10
> CANDY 5
> APPLE JUICE 10
> CANDY 5
> CANDY 5
> CANDY 5
> POTATO CHIPS 30
> 
> I'm expecting the following output
> BANANA FRIES 12
> POTATO CHIPS 60
> APPLE JUICE 20
> CANDY 20
> 
> However my code seems be returning incorrect value
> 
> #!/usr/bin/env python3
> 
> import sys
> import re
> from collections import OrderedDict
> 
> if __name__ == '__main__':
> 
>   od = OrderedDict()
>   recs = int(input())
> 
>   for _ in range(recs):
>     file_input = sys.stdin.readline().strip()
>     m = re.search(r"(\w.+)\s+(\d+)", file_input)
> 
>     if m:
>       if m.group(1) not in od.keys():
>         od[m.group(1)] = int(m.group(2))
>       else:
>         od[m.group(1)] += int(od.get(m.group(1),0))

Look closely at the line above. 

What value do you want to add to the current sum?
What value are you actually providing on the right side?

>   for k,v in od.items():
>     print(k,v)
> 
> What's really going on here?
> 
> $ cat groceries.txt | ./groceries.py
> BANANA FRIES 12
> POTATO CHIPS 60
> APPLE JUICE 20
> CANDY 40