CODEWITHSUNDEEP
pythonparsing
user3552506
user3552506

Reputation: 45

Parse math expression elements from string to list

if I have a 

string = '((a * 5) // ((10 - y) + z))'

and I just want to remove the a, 5, 10, y, z, and put them in 

lst1 = []

and I also want to remove the *, -, + and put them in

lst2 = []

What is the best way to do this?

Upvotes: 0

Views: 135

Answers (2)

user1438233
user1438233

Reputation: 1233

Please try the following:

import re
str = '((a * 5) // ((10 - y) + z))'

>> filter(None, re.split (r'[()*+ /-]', str))
['a', '5', '10', 'y', 'z']

>> filter(None, re.split ('[()0-9a-z ]', str))
['*', '//', '-', '+']

Upvotes: 0

Erik Kaplun
Erik Kaplun

Reputation: 38217

Using regular expressions (the re module):

>>> import re
>>> NAMES_AND_VALUES = re.compile(r'\w+')
>>> OPERATORS = re.compile(r'(?:\+|\*|\-|\/)+')

>>> string = '((a * 5) // ((10 - y) + z))'

>>> NAMES_AND_VALUES.findall(string)
['a', '5', '10', 'y', 'z']

>>> OPERATORS.findall(string)
['*', '//', '-', '+']

...and then of course you can just store these return values in lst1 and lst2 if you want. Or if lst1 and lst2 are pre-existing list objects, you can do lst1 += ... and lst2 += ....

Upvotes: 2

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