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  1. import re
  2.  
  3.  
  4. def tokenize(s):
  5.     return re.findall(r'\+|-|\*|=|\d+', s)
  6.  
  7.  
  8. def evaluate(stack):
  9.     return eval(''.join(stack))
  10.  
  11.  
  12. def calc(e):
  13.     stack = ['0']
  14.     for token in tokenize(e):
  15.         if token.isdigit():
  16.             if stack[-1].isdigit():
  17.                 stack[-1] = token
  18.             else:
  19.                 stack.append(token)
  20.         elif token in '+-*':
  21.             if stack[-1] in '+-*':
  22.                 stack[-1] = token
  23.             else:
  24.                 stack.append(token)
  25.         elif token == '=':
  26.             stack = [str(evaluate(stack))]
  27.     try:
  28.         return int(stack[-1])
  29.     except ValueError:
  30.         return evaluate(stack[:-1])
  31.  
  32.  
  33. def test():
  34.     assert calc("5") == 5
  35.     assert calc("5+") == 5
  36.     assert calc("5+3") == 3
  37.     assert calc("5+3=") == 8
  38.  
  39.     assert calc("5*-3=") == 2
  40.     assert calc("5-3+") == 2
  41.     assert calc("5-3*2=") == -1
  42.  
  43.     assert calc("") == 0
  44.     assert calc("-10=") == -10
  45.     assert calc("*10=") == 0
  46.  
  47.     assert calc("4+3=2=") == 2
  48.     assert calc("4+3=*2=") == 14
  49.  
  50.  
  51. if __name__ == '__main__':
  52.     test()
Success #stdin #stdout 0.03s 9984KB
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https://ideone.com/o0W21U
language:
Python 3 (python  3.12)
created:
10 years ago
visibility:
public

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