我想在Python中动态创建变量。有人有什么创造性的方法吗?


当前回答

在全局和/或本地名称空间中填充内容并不是一个好主意。使用字典太像其他语言了……D ['constant-key'] = value看起来很尴尬。Python是面向对象的。用一位大师的话来说:“命名空间是一个非常棒的想法——让我们做更多这样的事情吧!”""

是这样的:

>>> class Record(object):
...     pass
...
>>> r = Record()
>>> r.foo = 'oof'
>>> setattr(r, 'bar', 'rab')
>>> r.foo
'oof'
>>> r.bar
'rab'
>>> names = 'id description price'.split()
>>> values = [666, 'duct tape', 3.45]
>>> s = Record()
>>> for name, value in zip(names, values):
...     setattr(s, name, value)
...
>>> s.__dict__ # If you are suffering from dict withdrawal symptoms
{'price': 3.45, 'id': 666, 'description': 'duct tape'}
>>>

其他回答

注意:这应该被认为是一个讨论,而不是一个实际的答案。

一个近似的方法是在你想要创建变量的模块中操作__main__。例如,有一个b.py:

#!/usr/bin/env python
# coding: utf-8


def set_vars():
    import __main__
    print '__main__', __main__
    __main__.B = 1

try:
    print B
except NameError as e:
    print e

set_vars()

print 'B: %s' % B

运行它会输出

$ python b.py
name 'B' is not defined
__main__ <module '__main__' from 'b.py'>
B: 1

但是这种方法只适用于单个模块脚本,因为__main__ it导入将始终表示python正在执行的入口脚本的模块,这意味着如果B .py被其他代码涉及,B变量将在入口脚本的范围内创建,而不是在B .py本身中。假设有一个脚本a.py:

#!/usr/bin/env python
# coding: utf-8

try:
    import b
except NameError as e:
    print e

print 'in a.py: B', B

运行它会输出

$ python a.py
name 'B' is not defined
__main__ <module '__main__' from 'a.py'>
name 'B' is not defined
in a.py: B 1

注意,__main__被更改为'a.py'。

vars()['meta_anio_2012'] = 'translate'

关键字参数允许将变量从一个函数传递到另一个函数。通过这种方式,您可以使用字典的键作为变量名(可以在while循环中填充)。当它被调用时,字典名只需要在前面加上**。

# create a dictionary
>>> kwargs = {}
# add a key of name and assign it a value, later we'll use this key as a variable
>>> kwargs['name'] = 'python'

# an example function to use the variable
>>> def print_name(name):
...   print name

# call the example function
>>> print_name(**kwargs)
python

没有**,kwargs只是一个字典:

>>> print_name(kwargs)
{'name': 'python'}

free-dom:

import random

alphabet = tuple('abcdefghijklmnopqrstuvwxyz')

globkeys = globals().keys()
globkeys.append('globkeys') # because name 'globkeys' is now also in globals()

print 'globkeys==',globkeys
print
print "globals().keys()==",globals().keys()

for i in xrange(8):
    globals()[''.join(random.sample(alphabet,random.randint(3,26)))] = random.choice(alphabet)
del i

newnames = [ x for x in globals().keys() if x not in globkeys ]
print
print 'newnames==',newnames

print
print "globals().keys()==",globals().keys()

print
print '\n'.join(repr((u,globals()[u])) for u in newnames)

结果

globkeys== ['__builtins__', 'alphabet', 'random', '__package__', '__name__', '__doc__', 'globkeys']

globals().keys()== ['__builtins__', 'alphabet', 'random', '__package__', '__name__', 'globkeys', '__doc__']

newnames== ['fztkebyrdwcigsmulnoaph', 'umkfcvztleoij', 'kbutmzfgpcdqanrivwsxly', 'lxzmaysuornvdpjqfetbchgik', 'wznptbyermclfdghqxjvki', 'lwg', 'vsolxgkz', 'yobtlkqh']

globals().keys()== ['fztkebyrdwcigsmulnoaph', 'umkfcvztleoij', 'newnames', 'kbutmzfgpcdqanrivwsxly', '__builtins__', 'alphabet', 'random', 'lxzmaysuornvdpjqfetbchgik', '__package__', 'wznptbyermclfdghqxjvki', 'lwg', 'x', 'vsolxgkz', '__name__', 'globkeys', '__doc__', 'yobtlkqh']

('fztkebyrdwcigsmulnoaph', 't')
('umkfcvztleoij', 'p')
('kbutmzfgpcdqanrivwsxly', 'a')
('lxzmaysuornvdpjqfetbchgik', 'n')
('wznptbyermclfdghqxjvki', 't')
('lwg', 'j')
('vsolxgkz', 'w')
('yobtlkqh', 'c')

另一种方法:

import random

pool_of_names = []
for i in xrange(1000):
    v = 'LXM'+str(random.randrange(10,100000))
    if v not in globals():
        pool_of_names.append(v)

alphabet = 'abcdefghijklmnopqrstuvwxyz' 

print 'globals().keys()==',globals().keys()

print
for j in xrange(8):
    globals()[pool_of_names[j]] = random.choice(alphabet)
newnames = pool_of_names[0:j+1]

print
print 'globals().keys()==',globals().keys()

print
print '\n'.join(repr((u,globals()[u])) for u in newnames)

结果:

globals().keys()== ['__builtins__', 'alphabet', 'random', '__package__', 'i', 'v', '__name__', '__doc__', 'pool_of_names']


globals().keys()== ['LXM7646', 'random', 'newnames', 'LXM95826', 'pool_of_names', 'LXM66380', 'alphabet', 'LXM84070', '__package__', 'LXM8644', '__doc__', 'LXM33579', '__builtins__', '__name__', 'LXM58418', 'i', 'j', 'LXM24703', 'v']

('LXM66380', 'v')
('LXM7646', 'a')
('LXM8644', 'm')
('LXM24703', 'r')
('LXM58418', 'g')
('LXM84070', 'c')
('LXM95826', 'e')
('LXM33579', 'j')

在全局和/或本地名称空间中填充内容并不是一个好主意。使用字典太像其他语言了……D ['constant-key'] = value看起来很尴尬。Python是面向对象的。用一位大师的话来说:“命名空间是一个非常棒的想法——让我们做更多这样的事情吧!”""

是这样的:

>>> class Record(object):
...     pass
...
>>> r = Record()
>>> r.foo = 'oof'
>>> setattr(r, 'bar', 'rab')
>>> r.foo
'oof'
>>> r.bar
'rab'
>>> names = 'id description price'.split()
>>> values = [666, 'duct tape', 3.45]
>>> s = Record()
>>> for name, value in zip(names, values):
...     setattr(s, name, value)
...
>>> s.__dict__ # If you are suffering from dict withdrawal symptoms
{'price': 3.45, 'id': 666, 'description': 'duct tape'}
>>>