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I am trying to get all numerical value (integers,decimal,float,scientific notation) from an expression and want to differentiate them from digits that are not realy number but part of a name. For example in the expression below.

230FIC000.PV>=-2e3 211FIC00.PV <= 20 100fic>-20.4 tic200 >=45 tic100 <-2E-4 fic123 >1

the first 230 is not a numerical value as it is part of a tag (230FIC100.PV).

Using the web tool regexp.com I come up with the following expression that works for the expression above.

(?!\s)(?<!\w)[+-]?((\d+\.\d*)|(\.\d+)|(\d+))([eE][+-]?\d+)?(\s)|(?<!\w)[0-9]\d+(?<!\s)$

However when I try to use the above expression in python re.findall() I receive as result a list with 5 tuples with 6 elements on each.

import re
pat = r'(?!\s)(?<!\w)[+-]?((\d+\.\d*)|(\.\d+)|(\d+))([eE][+-]?\d+)?(\s)|(?<!\w)[0-9]\d+(?<!\s)$'
exp = '230FIC000.PV>=-2e3 211FIC00.PV <= 20 100fic>-20.4 tic200 >=45 tic100 <-2E-4 fic123 >1 '
matches = re.findall(pat,exp)

The result is

special variables
function variables
0:('2', '', '', '2', 'e3', ' ')
1:('20', '', '', '20', '', ' ')
2:('20.4', '20.4', '', '', '', ' ')
3:('45', '', '', '45', '', ' ')
4:('2', '', '', '2', 'e4', ' ')
len():5

I would like some help to undestand what is happening and if there is any way to get this done in a similar way that happen on the regexp.com.

Dariva
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1 Answers1

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This should take care of it. (All the items are strings)

import re

st = '230FIC000.PV>=-2e3 211FIC00.PV <= 20 100fic>-20.4 tic200 >=45 tic100 <-2E-4 fic123 >1'

re.findall(r'-?[0-9]+\.?[0-9]*(?:[Ee]\ *-?\ *[0-9]+)|-?\d+\.\d+|\b\d+\b', st)

referred: How to extract numbers from strings,

Extracting scientific numbers from string,

and Extracting decimal values from string

Ashwin Sankar
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