python中str（）和repr（）的区别

>>> s = 'Hello, world.'
>>> str(s)
'Hello, world.'
>>> repr(s)
"'Hello, world.'"
>>> str(1.0/7.0)
'0.142857142857'
>>> repr(1.0/7.0)
'0.14285714285714285'
>>> x = 10 * 3.25
>>> y = 200 * 200
>>> s = 'The value of x is ' + repr(x) + ', and y is ' + repr(y) + '...'
>>> print s
The value of x is 32.5, and y is 40000...
>>> # The repr() of a string adds string quotes and backslashes:
... hello = 'hello, world\n'
>>> hellos = repr(hello)
>>> print hellos
'hello, world\n'
>>> # The argument to repr() may be any Python object:
... repr((x, y, ('spam', 'eggs')))
"(32.5, 40000, ('spam', 'eggs'))"

一种是通过str函数，他会把值转换为合理形式的字符串，以便用户可以理解；另一种是通过repr函数，她会创建一个字符串，以合法的Python表达式的形式来表示值。

repr也可以做``反引号的实现。如果希望答应一个包含数字的句子，那么反引号就很有用了。比如：

>>> temp = 100
>>> print 'hello' + temp

Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    print 'hello' + temp
TypeError: cannot concatenate 'str' and 'int' objects
>>> print 'hello'+`temp`
hello100