Distinguish between numbers and letters with regular expressions

import re

def isd(N):
    return bool(re.compile("^[-+]?([0-9]+(\.[0-9]*)?|\.[0-9]+)([eE][-+]?[0-9]+)?$|nan$|^[-+]?inf$").match(N))

for i in ['-3.', '0.', '5..', '0.1', '1', '1e+2', 'b0', '0c', 'test','nan','1ee-3','1.3e-3','1.3e-3.','00.','5.0.','inf']:
	print('{0:9} {1}'.format(i,isd(i)))

-3.       True
0.        True
5..       False
0.1       True
1         True
1e+2      True
b0        False
0c        False
test      False
nan       True
1ee-3     False
1.3e-3    True
1.3e-3.   False
00.       True
5.0.      False
inf       True

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