python数据类型转换 python字符串转浮点数 python字符串转float

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转载 http://www.cnblogs.com/dabiao/archive/2010/03/07/1680096.html

一、int函数能够
（1）把符合数学格式的数字型字符串转换成整数
（2）把浮点数转换成整数，但是只是简单的取整，而非四舍五入。

举例：

 1 aa = int("124")    #Correct 2  print "aa = ", aa  #result=124 3  bb = int(123.45) #correct 4  print "bb = ", bb #result=123 5  cc = int("-123.45")  #Error,Can't Convert to int 6  print "cc = ",cc 7 dd = int("34a")    #Error,Can't Convert to int 8 print "dd = ",dd 9 ee = int("12.3") #Error,Can't Convert to int10 print ee 11

二、float函数将整数和字符串转换成浮点数。

举例：

 1 aa = float("124")     #Correct 2 print "aa = ", aa     #result = 124.0  3 bb = float("123.45")  #Correct 4 print "bb = ", bb     #result = 123.45 5 cc = float(-123.6)    #Correct 6 print "cc = ",cc      #result = -123.6 7 dd = float("-123.34") #Correct 8 print "dd = ",dd      #result = -123.34 9 ee = float('123v')    #Error,Can't Convert to float10 print ee

三、str函数将数字转换成字符

举例：

 1 aa = str(123.4)     #Correct 2 print aa            #result = '123.4' 3 bb = str(-124.a)    #SyntaxError: invalid syntax 4 print bb 5 cc = str("-123.45") #correct 6 print cc            #result = '-123.45' 7 dd = str('ddd')     #correct 8 print dd            #result = ddd 9 ee = str(-124.3)    #correct10 print ee            #result = -124.3

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