python内置方法、模块讲解（五）

• 2016-02-28 00:13:24
• 1258
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• python
• authen

十六、complie方法

1、定义：

compile(...)
    compile(source, filename, mode[, flags[, dont_inherit]]) -> code object

    Compile the source string (a Python module, statement or expression)
    into a code object that can be executed by the exec statement or eval().
    The filename will be used for run-time error messages.
    The mode must be 'exec' to compile a module, 'single' to compile a
    single (interactive) statement, or 'eval' to compile an expression.
    The flags argument, if present, controls which future statements influence
    the compilation of the code.
    The dont_inherit argument, if non-zero, stops the compilation inheriting
    the effects of any future statements in effect in the code calling
    compile; if absent or zero these statements do influence the compilation,
    in addition to any features explicitly specified.

2、解释：将source编译为代码或者AST对象。代码对象能够通过exec语句来执行或者eval()进行求值。

3、举例：

例1：
>>> code = "for i in range(0, 10): print i"
>>> cmpcode = compile(code, '', 'exec')
>>> exec cmpcode
0
1
2
3
4
5
6
7
8
9
>>> str = "3 * 4 + 5"
>>> a = compile(str,'','eval')
>>> eval(a)
17
例2：
test.cfg内容如下：
SQLALCHEMY_POOL_RECYCLE = 10
SQLALCHEMY_ECHO = False
filename = 'test.cfg'
_dict = {}
with open(filename) as config_file:
    code_obj = compile(config_file.read(), '', 'exec')
exec(code_obj, _dict)
print _dict.get('SQLALCHEMY_POOL_RECYCLE')
print _dict.get('SQLALCHEMY_ECHO')

输出：
10
False
因此_dict 变量获得了test.cfg文件中的配置信息

十七、complex类

1、定义：

class complex(object)
 |  complex(real[, imag]) -> complex number
 |
 |  Create a complex number from a real part and an optional imaginary part.
 |  This is equivalent to (real + imag*1j) where imag defaults to 0.

2、解释：生成一个复数

3、举例：

>>> complex(1,5)
(1+5j)
>>> complex(1)
(1+0j)
>>> complex(1,-5)
(1-5j)