Parsing a list of single numbers and number ranges

Question

I have input of a string containing a single number (like: \3ドル\$) or a range (like: \1ドル-5\$). Sample input, all together, looks like: "1-5,3,15-16", and sample output for that input looks like "1,2,3,4,5,15". Output doesn't need to be sorted.

I built something to parse this, but it's ugly. How can I improve this?

from itertools import chain
def giveRange(numString:str):
 z=numString.split("-")
 if(len(z)==1):
 return [int(z[0])]
 elif(len(z)==2):
 return list(range(int(z[0]),int(z[1])+1))
 else:
 raise IndexError("TOO MANY VALS!")
def unpackNums(numString:str):
 rList=[]
 rList.extend(set(chain(*map(giveRange,numString.split(",")))))
 return rList
unpackNums("1-2,30-50,1-10")

Answer 1

Disclaimer: I'm not a Python programmer!

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Your code isn't that bad. It's readable enough for me to understand it. B+ for readability!

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Currently, you have this function:

def giveRange(numString:str):
 z=numString.split("-")
 if(len(z)==1):
 return [int(z[0])]
 elif(len(z)==2):
 return list(range(int(z[0]),int(z[1])+1))
 else:
 raise IndexError("TOO MANY VALS!")

Why don't you simply store the length in a variable?

Like this:

length=len(z)
if(length==1):
 return [int(z[0])]
elif(length==2):
 return list(range(int(z[0]),int(z[1])+1))
else:
 raise IndexError("TOO MANY VALS!")

Now, you don't have to calculate the length twice, only once.

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The name z is a really bad name. Better names would be numbers, pieces or something similar.

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Looking at the definition of chain(), it seems to accept any iterable, which a range() happens to be. So, you probably don't need that list(), leaving this:

return range(int(z[0]),int(z[1])+1)

---

On your function unpackNums instead of creating an empty set(), you could use the a set comprehension:

def unpackNums(numString:str):
 return {x for x in set(chain(*map(giveRange,numString.split(","))))}

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If you notice any inaccuracies, please comment.

Answer 2

Since the whole exercise is a string-transformation problem, I suggest performing it using a regex substitution.

import re
def expand_ranges(s):
 return re.sub(
 r'(\d+)-(\d+)',
 lambda match: ','.join(
 str(i) for i in range(
 int(match.group(1)),
 int(match.group(2)) + 1
 ) 
 ), 
 s
 )

I think that expand_ranges would be a more descriptive name than unpackNums.

• Android Control: This solution does not remove duplicate values. An input of "1-2,30-50,1-10" will yield an output of 1,2,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,1,2,3,4,5,6,7,8,9,10