How can I store an Expression in List with proper Separation?

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I am trying Parenthesis Matching (Unbalanced or Balanced ) Program using stack and Have a Doubt in this...

How Can i store an Expression in a List with Proper Separation ..

i was tried by storing the expression as String but also there was a problem like if an user give input like

exp = "2*3+11+2"

for i in exp:

    print(i)
Output :
for the 11 it will print 1 1 (two times)

How can i store in List.. i mean if an User give Input

like = (2*3)+(4*60)/3 it should store like [(,2,*,3,),+,(,4,*,60,),/,3] so that i can traverse through it properly and check for the ( or ) parenthesis

i can do it by space input like 2 + 3 (by using split() function ) but what to do if an user is not giving input by spacing ?

data-structures python-3.x list python
2 Answers

Do you mean by:

import re
exp = "2*3+11+2"
print([i for i in re.split('(\D)', exp) if i.strip() != ''])

Output:

['2', '*', '3', '+', '11', '+', '2']
user_87083640

This isn't as short and concise as the other suggested answers, but it may be more understandable, and it uses the builtin tokenize library, so someone else has already solved the problems for you. Here's an example boiled down from the tokenize Python docs

from tokenize import tokenize, ENCODING, ENDMARKER, NEWLINE
from io import BytesIO
def tok_string(exp: str):
    token_gen = tokenize(BytesIO(exp.encode("utf-8")).readline)
    result = list()
    for token in token_gen:
        print(token)
        if token.type not in (ENCODING, ENDMARKER, NEWLINE):
            result.append(token.string)
    return result

print("FIRST EXAMPLE")
print(tok_string("2*3 +11+2"))
print("\n SECOND EXAMPLE")
print(tok_string("(2*3)+(4*60)/3"))

generates the output:

FIRST EXAMPLE
TokenInfo(type=62 (ENCODING), string='utf-8', start=(0, 0), end=(0, 0), line='')   
TokenInfo(type=2 (NUMBER), string='2', start=(1, 0), end=(1, 1), line='2*3 +11+2') 
TokenInfo(type=54 (OP), string='*', start=(1, 1), end=(1, 2), line='2*3 +11+2')    
TokenInfo(type=2 (NUMBER), string='3', start=(1, 2), end=(1, 3), line='2*3 +11+2') 
TokenInfo(type=54 (OP), string='+', start=(1, 4), end=(1, 5), line='2*3 +11+2')    
TokenInfo(type=2 (NUMBER), string='11', start=(1, 5), end=(1, 7), line='2*3 +11+2')
TokenInfo(type=54 (OP), string='+', start=(1, 7), end=(1, 8), line='2*3 +11+2')
TokenInfo(type=2 (NUMBER), string='2', start=(1, 8), end=(1, 9), line='2*3 +11+2')
TokenInfo(type=4 (NEWLINE), string='', start=(1, 9), end=(1, 10), line='')
TokenInfo(type=0 (ENDMARKER), string='', start=(2, 0), end=(2, 0), line='')
['2', '*', '3', '+', '11', '+', '2']

 SECOND EXAMPLE
TokenInfo(type=62 (ENCODING), string='utf-8', start=(0, 0), end=(0, 0), line='')
TokenInfo(type=54 (OP), string='(', start=(1, 0), end=(1, 1), line='(2*3)+(4*60)/3')
TokenInfo(type=2 (NUMBER), string='2', start=(1, 1), end=(1, 2), line='(2*3)+(4*60)/3')
TokenInfo(type=54 (OP), string='*', start=(1, 2), end=(1, 3), line='(2*3)+(4*60)/3')
TokenInfo(type=2 (NUMBER), string='3', start=(1, 3), end=(1, 4), line='(2*3)+(4*60)/3')
TokenInfo(type=54 (OP), string=')', start=(1, 4), end=(1, 5), line='(2*3)+(4*60)/3')
TokenInfo(type=54 (OP), string='+', start=(1, 5), end=(1, 6), line='(2*3)+(4*60)/3')
TokenInfo(type=54 (OP), string='(', start=(1, 6), end=(1, 7), line='(2*3)+(4*60)/3')
TokenInfo(type=2 (NUMBER), string='4', start=(1, 7), end=(1, 8), line='(2*3)+(4*60)/3')
TokenInfo(type=54 (OP), string='*', start=(1, 8), end=(1, 9), line='(2*3)+(4*60)/3')
TokenInfo(type=2 (NUMBER), string='60', start=(1, 9), end=(1, 11), line='(2*3)+(4*60)/3')
TokenInfo(type=54 (OP), string=')', start=(1, 11), end=(1, 12), line='(2*3)+(4*60)/3')
TokenInfo(type=54 (OP), string='/', start=(1, 12), end=(1, 13), line='(2*3)+(4*60)/3')
TokenInfo(type=2 (NUMBER), string='3', start=(1, 13), end=(1, 14), line='(2*3)+(4*60)/3')
TokenInfo(type=4 (NEWLINE), string='', start=(1, 14), end=(1, 15), line='')
TokenInfo(type=0 (ENDMARKER), string='', start=(2, 0), end=(2, 0), line='')
['(', '2', '*', '3', ')', '+', '(', '4', '*', '60', ')', '/', '3']

As you can see, there's a lot more information provided by the tokenize-er that you may want to take advantage of.

user_48022590
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