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问题描述

是否有可能在Python中创建一个维护变量

值的函数?


这样的东西:


globe = 0;

def myFun():

globe = globe + 1

返回地球


显然不可能那样做。我认为它可能是通过在变量前加上一些包上下文来完成的。


Python文档非常笨拙。在python doc中哪里是一个程序员

应该读一下Python中的包/模块系统如何工作?

(除了触及它的教程)


Xah



is it possible in Python to create a function that maintains a variable
value?

something like this:

globe=0;
def myFun():
globe=globe+1
return globe

apparently it can''t be done like that. I thought it can probably be
done by prefixing the variable with some package context...

the Python doc is quite stilted. Where in the python doc is a programer
supposed read about how the package/module system in Python works?
(besides the tutorial that touches it)

Xah
xa*@xahlee.org
http://xahlee.org/PageTwo_dir/more.html

推荐答案




简短的回答是使用全局声明:


globe = 0

def myFun():

全球地球仪

globe = globe + 1

返回地球仪



globe = 0

globe = myfun(全球)

def myFun( var):

返回var + 1


更优雅的是使用类和类属性而不是

全局变量。


-pu



The short answer is to use the global statement:

globe=0
def myFun():
global globe
globe=globe+1
return globe

more elegant is:

globe=0
globe=myfun(globe)
def myFun(var):
return var+1

and still more elegant is using classes and class attributes instead of
global variables.

-pu





除非您必须告诉它明确地表示你是使用全局的b $ b,否则Python会看到globe =并决定

你想要''globe''是一个局部变量。


globe = 0

def myFun():

全球全球

globe = globe + 1

返回地球


或者,换行值在一个可变的类型,所以你不必做任务

一个任务(并可以在嵌套范围内使用它):


globe = [0]

def myFun():

globe [0] + = 1

返回地球[0]


你可以用来隐藏函数外部代码的静态的hack滥用这个默认参数在定义时计算的事实:


def myFun(globe = [0]):

globe [0] + = 1

返回globe [0]


对于更复杂的情况,最好明确并使用

对象:


类计数器:

def __init__ (个体经营):

self.globe = 0

def count(个体经营):

self.globe + = 1

返回self.globe


myFun = Counter()。count


-

Andrew Clover

mailto:an*@doxdesk.com




This would work except that you have to tell it explicitly that you''re
working with a global, otherwise Python sees the "globe=" and decides
you want ''globe'' be a local variable.

globe= 0
def myFun():
global globe
globe= globe+1
return globe

Alternatively, wrap the value in a mutable type so you don''t have to do
an assignment (and can use it in nested scopes):

globe= [ 0 ]
def myFun():
globe[0]+= 1
return globe[0]

A hack you can use to hide statics from code outside the function is to
abuse the fact that default parameters are calcuated at define-time:

def myFun(globe= [ 0 ]):
globe[0]+= 1
return globe[0]

For more complicated cases, it might be better to be explicit and use
objects:

class Counter:
def __init__(self):
self.globe= 0
def count(self):
self.globe+= 1
return self.globe

myFun= Counter().count

--
Andrew Clover
mailto:an*@doxdesk.com
http://www.doxdesk.com/





这让我很难过。什么是myfun()?什么是var意图?


肯特



This mystifies me. What is myfun()? What is var intended to be?

Kent


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09-18 03:38