How to extract part of a string

import re
s = '-1007.88670550662*p**(-1.0) + 67293.8347365694*p**(-0.416543501823503)'
pattern = r'-?\d+\.\d*'  

a,_,b,c = re.findall(pattern,s)
print(a, b, c)

      

        
        
        
      

    

Output

('-1007.88670550662', '67293.8347365694', '-0.416543501823503')

      

        
        
        
      

    

s

- this is your test line, and what is not pattern

- regular expression pattern, we are looking for float, and as soon as we find them with the help findall()

we return them back in a

, b

,c

Note. This method only works if your string is in the format that you specified. otherwise you can play with the pattern however you want.

Edit like most of the people mentioned in the comments, if you need to add +

before your positive numbers you can use this templater'[-+]?\d+\.\d*'

Of course a module re

can be used to do this, although as noted in some of the comments on the other answers, corner cases can be interesting - decimal points, plus and minus signs, etc. This can be even more interesting; for example, can your number be imaginary?

In any case, if your string is always a valid Python expression, you can use Python's built-in tools to process it. Here is a good general explanation regarding the ast class NodeVisitor

. Using it for your example is pretty simple:

import ast

x = "-1007.88670550662*p**(-1.0) + 67293.8347365694*p**(-0.416543501823503)"

def getnums(s):
    result = []
    class GetNums(ast.NodeVisitor):
        def visit_Num(self, node):
            result.append(node.n)
        def visit_UnaryOp(self, node):
            if (isinstance(node.op, ast.USub) and
                isinstance(node.operand, ast.Num)):
                result.append(-node.operand.n)
            else:
                ast.NodeVisitor.generic_visit(self, node)
    GetNums().visit(ast.parse(s))
    return result

print(getnums(x))

      

        
        
        
      

    

This will return a list with all the numbers in your expression:

[-1007.88670550662, -1.0, 67293.8347365694, -0.416543501823503]

      

        
        
        
      

    

This method visit_UnaryOp

is only required for Python 3.x.

You can use something like:

import re
a,_,b,c = re.findall(r"[\d\-.]+", subject)
print(a,b,c)

      

        
        
        
      

    

Demo