<p>一个基于@alexce示例的简单示例:</p>
<pre><code>>>> pi = 22/7
>>> pi
3
</code></pre>
<p>当前在全局命名空间中定义的变量:</p>
<pre><code>>>> vars()
{'__builtins__': <module '__builtin__' (built-in)>, '__name__': '__main__', 'pi': 3, '__doc__': None, '__package__': None}
</code></pre>
<p>现在我们进行基于<code>*</code>的导入:</p>
<pre><code>>>> from math import *
</code></pre>
<p>来自<code>math</code>的新<code>pi</code>替换旧的<code>pi</code></p>
<pre><code>>>> pi
3.141592653589793
</code></pre>
<p>现在,全局名称空间充满了数学模块的变量:</p>
<pre><code>>>> vars()
{'pow': <built-in function pow>, 'fsum': <built-in function fsum>, 'cosh': <built-in function cosh>, 'ldexp': <built-in function ldexp>, 'hypot': <built-in function hypot>, 'acosh': <built-in function acosh>, 'tan': <built-in function tan>, 'asin': <built-in function asin>, 'isnan': <built-in function isnan>, 'log': <built-in function log>, 'fabs': <built-in function fabs>, 'floor': <built-in function floor>, 'atanh': <built-in function atanh>, 'sqrt': <built-in function sqrt>, '__package__': None, 'frexp': <built-in function frexp>, 'factorial': <built-in function factorial>, 'degrees': <built-in function degrees>, 'pi': 3.141592653589793, 'log10': <built-in function log10>, '__doc__': None, 'asinh': <built-in function asinh>, 'fmod': <built-in function fmod>, 'atan': <built-in function atan>, '__builtins__': <module '__builtin__' (built-in)>, 'copysign': <built-in function copysign>, 'cos': <built-in function cos>, 'ceil': <built-in function ceil>, 'atan2': <built-in function atan2>, 'isinf': <built-in function isinf>, 'sinh': <built-in function sinh>, '__name__': '__main__', 'trunc': <built-in function trunc>, 'expm1': <built-in function expm1>, 'e': 2.718281828459045, 'tanh': <built-in function tanh>, 'radians': <built-in function radians>, 'sin': <built-in function sin>, 'lgamma': <built-in function lgamma>, 'erf': <built-in function erf>, 'erfc': <built-in function erfc>, 'modf': <built-in function modf>, 'exp': <built-in function exp>, 'acos': <built-in function acos>, 'log1p': <built-in function log1p>, 'gamma': <built-in function gamma>}
</code></pre>
<p>因此,这样的导入将替换已在全局命名空间中定义的具有相同名称的所有变量。你知道吗</p>
<p>从<a href="http://docs.python.org/2/tutorial/modules.html#more-on-modules" rel="nofollow">docs</a>:</p>
<blockquote>
<p>Note that in general the practice of importing <code>*</code> from a module or
package is <strong>frowned</strong> upon, since it often causes poorly readable code.
However, it is okay to use it to save typing in interactive sessions.</p>
</blockquote>