数据转换

1.int(x[,base])
(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。

     aa = int("1234")
     print "aa = ", aa

     bb = int(123.45)
     print "bb = ",bb

     cc = int("1234.5")
     print "cc = ", cc      #双引号内的数不能带有小数点。

输出： aa = 1234
bb = 123
cc会报错

2.long(x[,base])
与int语句的操作方式一样

3.字符串转为浮点数
float(x) 将整数x或字符串x转换成浮点数

 aa = float("123")
 print "aa = ", aa

 bb = float("123.45")
 print "bb = ", bb

cc = float("-123.34")
print "cc = ", cc

dd = float("123a")         #双引号内不能加字母
print "dd = ", dd

输出：
aa = 123.0
bb = 123.45
cc = -123.34
dd会报错

4.str(x) 数字转换为字符串类型

aa = str("123.4")
print "aa = ", aa

bb = str(-123.5)
print "bb = ",bb

cc = str("-1234.5")
print "cc = ", cc

dd = str("aaa")
print "dd = ", dd
输出：
aa = 123.4
bb = -123.5
cc = -1234.5
dd = aaa