python内置方法、模块讲解（七）

• 2016-03-02 23:42:00
• 1150
• 0

• python
• authen

二十二、divmod方法

1、定义：

divmod(...)
    divmod(x, y) -> (quotient, remainder)

    Return the tuple ((x-x%y)/y, x%y).  Invariant: div*y + mod == x.

2、解释：以元组的形式返回x除以y的商和余数

3、举例：

>>> divmod(5,2)
(2, 1)
>>> divmod(5,0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ZeroDivisionError: integer division or modulo by zero
>>> divmod(0,5)
(0, 0)

二十三、enumerate类

1、定义：

class enumerate(object)
 |  enumerate(iterable[, start]) -> iterator for index, value of iterable
 |
 |  Return an enumerate object.  iterable must be another object that supports
 |  iteration.  The enumerate object yields pairs containing a count (from
 |  start, which defaults to zero) and a value yielded by the iterable argument. |  enumerate is useful for obtaining an indexed list:
 |      (0, seq[0]), (1, seq[1]), (2, seq[2]), ...

2、解释：返回带计数值（从0开始）和迭代值的迭代对象，如：(0, seq[0]), (1, seq[1]), (2, seq[2]),...

​3、举例：

>>> a = range(5,10)
>>> for index, value in enumerate(a):
...     print index, value
...
0 5
1 6
2 7
3 8
4 9

二十四、eval方法

1、定义：

eval(...)
    eval(source[, globals[, locals]]) -> value

    Evaluate the source in the context of globals and locals.
    The source may be a string representing a Python expression
    or a code object as returned by compile().
    The globals must be a dictionary and locals can be any mapping,
    defaulting to the current globals and locals.
    If only globals is given, locals defaults to it.

2、解释：在全局变量、局部变量环境中运行源代码source，source可以是python表达式、或者被complie方法编译后的返回对象。

3、举例：

>>> a = '1 if True else 0'
>>> eval(a)
1
注：关于运行complie返回对象的例子可以查看讲解compile那篇：http://www.aoyanming.com/blog/display/12