★★★★[转载]Python学习笔记一:数据类型转换★★★★

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 int
10 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 float
10 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)    #correct
10 print ee            #result = -124.3