修改字符串的函数 [英] function that modifies a string

问题描述

我想创建一个执行以下操作的函数。我将其称为

thefunc。

> > s =" Char"
thefunc（s）
s

''|| Char> ;>''


我尝试了以下


def thefunc（s）：

s =" ||" + s +">>"


问题是，如果我在将函数

应用到它之后查看字符串，那么没有修改。我意识到我在变量的

范围内遇到了问题。函数s中的字符串是

函数的本地字符串，因此我不会更改输入的字符串，而是更改

副本。我似乎无法弄清楚如何得到我想要的东西。感谢

你的时间。

解决方案

greenflame写道：

我想创建一个执行以下操作的函数。我将其称为

thefunc。

> s =" Char"
thefunc（s）
s

''|| Char>>''


我尝试了以下


def thefunc（s）：

s =" ||" + s +">>"


问题是，如果我在将函数

应用到它之后查看字符串，那么没有修改。我意识到我在变量的

范围内遇到了问题。函数s中的字符串是

函数的本地字符串，因此我不会更改输入的字符串，而是更改

副本。我似乎无法弄清楚如何得到我想要的东西。感谢

你的时间。

你不能直接做你想做的事。字符串是

不可变对象。一旦创建了一个字符串，该字符串就不能被修改为
。当您对字符串进行操作时，会产生不同的

字符串。对字符串进行操作的函数应返回其值：

>> def thefunc（ s）：

.... return''||''+ s +''>>''

....

>> s =' 'Char''
s = thefunc（s）
s

''|| Char>> ;''


有/几个hacks会做你想要的。但是，如果你确实需要它，那么你可能需要重新考虑你的程序设计。

记住，你不能改变字符串，因为字符串是不可变的！你

可以改变一个变量来绑定另一个字符串。在下面的

示例中，s会反弹到新字符串，而t保留原始的

字符串值：

>> def changeString（varName）：

.... globalDict = globals（）

.... globalDict [varName] =''||''+ globalDict [varName] +''>>''

....返回

....

>> s =''Char''
t = s
changeString（'s''）
s

''|| Char>>''

>> t

''Char''


另请注意，这仅影响全局范围内的变量。我希望这会有所帮助！


- 贾森

greenflame写道：

我想创建一个执行以下操作的函数。我将其称为

thefunc。

> s =" Char"
thefunc（s）
s

''|| Char>>''


我尝试了以下


def thefunc（s）：

s =" ||" + s +">>"


问题是，如果我在将函数

应用到它之后查看字符串，那么没有修改。我意识到我在变量的

范围内遇到了问题。函数s中的字符串是

函数的本地字符串，因此我不会更改输入的字符串，而是更改

副本。我似乎无法弄清楚如何得到我想要的东西。感谢

你的时间。

快速入侵


def thefunc（s）：

return s =" | |" + s +">>"

>> s =" ;你好
s = thefunc（s）
print s

|| hello>>

- 欢呼

Jason写道：

>

你无法直接做你想做的事。字符串是

不可变对象。一旦创建了一个字符串，该字符串就不能被修改为
。当您对字符串进行操作时，会产生不同的

字符串。对字符串进行操作的函数应返回其值：

> def thefunc（s）：

...返回''||''+ s +''>>''

...
< blockquote class =post_quotes>

> s =''Char''
s = thefunc（s）
s

''|| Char>>''


有/有几个hacks会做你想要的。但是，如果你确实需要它，那么你可能需要重新考虑你的程序设计。

记住，你不能改变字符串，因为字符串是不可变的！你

可以改变一个变量来绑定另一个字符串。在下面的

示例中，s会反弹到新字符串，而t保留原始的

字符串值：

> def changeString（varName）：

... globalDict = globals（）

... globalDict [varName] =''||''+ globalDict [varName] +''>>''

...返回

...

> s =''Char''
t = s
changeString （'s''）s

''|| Char>>''

> t

''Char''


另请注意，这仅影响全局范围内的变量。我希望这会有所帮助！


--Jason

好​​的让我看看是否我明白。 globalDict只是一个字典

包含全局变量的名称作为键，它们的

值作为字典的值？因此，输入变量是否像对待全局变量一样被视为
？

I want to make a function that does the following. I will call it
thefunc for short.

>>s = "Char"
thefunc(s)
s

''||Char>>''

I tried the following

def thefunc(s):
s = "||" + s + ">>"

The problem is that if I look at the string after I apply the function
to it, it is not modified. I realized that I am having issues with the
scope of the variables. The string in the function, s, is local to the
function and thus I am not changing the string that was inputed, but a
copy. I cannot seem to figure out how to get what I want done. Thank
you for your time.

解决方案

greenflame wrote:

I want to make a function that does the following. I will call it
thefunc for short.

>s = "Char"
thefunc(s)
s

''||Char>>''

I tried the following

def thefunc(s):
s = "||" + s + ">>"

The problem is that if I look at the string after I apply the function
to it, it is not modified. I realized that I am having issues with the
scope of the variables. The string in the function, s, is local to the
function and thus I am not changing the string that was inputed, but a
copy. I cannot seem to figure out how to get what I want done. Thank
you for your time.

You cannot do what you are trying to do directly. Strings are
immutable objects. Once a string is created, that string cannot be
modified. When you operate on a string, you produce a different
string. Functions which operate on a string should return their value:

>>def thefunc(s):

.... return ''||'' + s + ''>>''
....

>>s = ''Char''
s = thefunc(s)
s

''||Char>>''

There /are/ a few hacks which will do what you want. However, if you
really need it, then you probably need to rethink your program design.
Remember, you can''t change a string since a string is immutable! You
can change a variable to bind to another string. In the following
example, s gets rebound to the new string while t keeps the original
string value:

>>def changeString(varName):

.... globalDict = globals()
.... globalDict[varName] = ''||'' + globalDict[varName] + ''>>''
.... return
....

>>s = ''Char''
t = s
changeString(''s'')
s

''||Char>>''

>>t

''Char''

Further note that this only affects variables in the global scope. I
hope this helps!

--Jason

greenflame wrote:

I want to make a function that does the following. I will call it
thefunc for short.

>s = "Char"
thefunc(s)
s

''||Char>>''

I tried the following

def thefunc(s):
s = "||" + s + ">>"

The problem is that if I look at the string after I apply the function
to it, it is not modified. I realized that I am having issues with the
scope of the variables. The string in the function, s, is local to the
function and thus I am not changing the string that was inputed, but a
copy. I cannot seem to figure out how to get what I want done. Thank
you for your time.

quick hack

def thefunc(s):
return s = "||" + s + ">>"

>>s = "hello"
s = thefunc(s)
print s

||hello>>
--Cheers

Jason wrote:

>
You cannot do what you are trying to do directly. Strings are
immutable objects. Once a string is created, that string cannot be
modified. When you operate on a string, you produce a different
string. Functions which operate on a string should return their value:

>def thefunc(s):

... return ''||'' + s + ''>>''
...

>s = ''Char''
s = thefunc(s)
s

''||Char>>''

There /are/ a few hacks which will do what you want. However, if you
really need it, then you probably need to rethink your program design.
Remember, you can''t change a string since a string is immutable! You
can change a variable to bind to another string. In the following
example, s gets rebound to the new string while t keeps the original
string value:

>def changeString(varName):

... globalDict = globals()
... globalDict[varName] = ''||'' + globalDict[varName] + ''>>''
... return
...

>s = ''Char''
t = s
changeString(''s'')
s

''||Char>>''

>t

''Char''

Further note that this only affects variables in the global scope. I
hope this helps!

--Jason

Ok so let me see if I understand. The globalDict is just a dictionary
containing the name of the global variables as the keys and their
values as the values of the dictionary? Thus the inputed variable is
treated like a global variable?

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