如何在Python中将字符串解析为float或int？
在Python中，我怎样才能解析一个数字字符串像"545.2222"到它相应的浮点值542.2222 ？ 或者将字符串"31"解析为一个整数31 ？
我只想知道如何将一个浮点string解析为一个float ，然后（单独）将一个int string解析为一个int 。
>>> a = "545.2222"
>>> float(a)
545.22220000000004
>>> int(float(a))
545
def num(s):
try:
return int(s)
except ValueError:
return float(s)
检查字符串是否为float的Python方法：
def isfloat(value):
try:
float(value)
return True
except:
return False
该函数的名称越长越准确： isConvertibleToFloat(value)
什么是，而不是Python中的float可能会让你感到惊讶：
val isfloat(val) Note
-------------------- ---------- --------------------------------
"" False Blank string
"127" True Passed string
True True Pure sweet Truth
"True" False Vile contemptible lie
False True So false it becomes true
"123.456" True Decimal
" -127 " True Spaces trimmed
"tn12rn" True whitespace ignored
"NaN" True Not a number
"NaNanananaBATMAN" False I am Batman
"-iNF" True Negative infinity
"123.E4" True Exponential notation
".1" True mantissa only
"1,234" False Commas gtfo
u'x30' True Unicode is fine.
"NULL" False Null is not special
0x3fade True Hexidecimal
"6e7777777777777" True Shrunk to infinity
"1.797693e+308" True This is max value
"infinity" True Same as inf
"infinityandBEYOND" False Extra characters wreck it
"12.34.56" False Only one dot allowed
u'四' False Japanese '4' is not a float.
"#56" False Pound sign
"56%" False Percent of what?
"0E0" True Exponential, move dot 0 places
0**0 True 0___0 Exponentiation
"-5e-5" True Raise to a negative number
"+1e1" True Plus is OK with exponent
"+1e1^5" False Fancy exponent not interpreted
"+1e1.3" False No decimals in exponent
"-+1" False Make up your mind
"(1)" False Parenthesis is bad
你以为你知道什么是数字？ 你不如你想象的那么好！ 不是很大的惊喜。
链接地址: http://www.djcxy.com/p/1321.html