为什么这个正则表达式不能在python中工作？ 它有效且在RegExr上正常工作

Question

I have this regex with I'm using to split a string into tokens I can process later. I made it using RegExr (online tool) and it works fine there, but I can't get it to work in python. I'm using this now to print the matches.

sunit = "A^2.1e2 m/s -180.2"
pat = "[A-Za-z]+(\^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?)?|\/|\*|[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?"
Terms = re.findall(pat,sunit)
print Terms

The regex should be matching:

A^2.1e2
m
/
s
-180.2

Answer 1

Solved it. Using 're.finditer()' instead of 're.findall()' seems to work. Here is what I came up with now. Sorry for bothering you, I should have been able solved this a long time ago.

sunit = r"A^2.1e2 m/s -180.2"
pat = r"[A-Za-z]+(\^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?)?|\/|\*|[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?"
Terms = re.finditer(pat,sunit)
for m in Terms:
    print m.group(0)

Answer 2

You have group captures (...) in your regex. If you do not wish to capture the groups, then just remove the brackets from there. Or use ?: inside the bracket to ignore it, example (?:...) . I have changed your regex and it will work with re.findall

pat = "[A-Za-z]+(?:\^[-+]?[0-9]*\.?[0-9]+(?:[eE][-+]?[0-9]+)?)?|\/|\*|[-+]?[0-9]*\.?[0-9]+(?:[eE][-+]?[0-9]+)?"
                 ^^                       ^^                                               ^^