来自的一个正则表达式perldoc perlretut
:
import re re_float = re.compile("""(?x) ^ [+-]?\ * # first, match an optional sign *and space* ( # then match integers or f.p. mantissas: \d+ # start out with a ... ( \.\d* # mantissa of the form a.b or a. )? # ? takes care of integers of the form a |\.\d+ # mantissa of the form .b ) ([eE][+-]?\d+)? # finally, optionally match an exponent $""") m = re_float.match("4.5") print m.group(0) # -> 4.5
要从更大的字符串中提取数字:
s = """4.5 abc -4.5 abc - 4.5 abc + .1e10 abc . abc 1.01e-2 abc 1.01e-.2 abc 123 abc .123""" print re.findall(r"[+-]? *(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?", s) # -> ['4.5', '-4.5', '- 4.5', '+ .1e10', ' 1.01e-2', # ' 1.01', '-.2', ' 123', ' .123']
这是简单的方法.不要将regex用于内置类型.
try: x = float( someString ) except ValueError, e: # someString was NOT floating-point, what now?
对于parse int和float(点分隔符)值:
re.findall( r'\d+\.*\d*', 'some 12 12.3 0 any text 0.8' )
结果:
['12', '12.3', '0', '0.8']