.join()方法具体做什么?

I'm pretty new to Python and am completely confused by .join() which I have read is the preferred method for concatenating strings.

我对Python非常陌生，并且完全被.join()所迷惑，我已经读过它是连接字符串的首选方法。

I tried:

我试着:

strid = repr(595)
print array.array('c', random.sample(string.ascii_letters, 20 - len(strid)))
    .tostring().join(strid)

and got something like:

和有类似:

5wlfgALGbXOahekxSs9wlfgALGbXOahekxSs5

Why does it work like this? Shouldn't the 595 just be automatically appended?

为什么它是这样工作的?595不是应该自动添加吗?

6 个解决方案

#1

256

Look carefully at your output:

仔细看看你的输出:

5wlfgALGbXOahekxSs9wlfgALGbXOahekxSs5
^                 ^                 ^

I've highlighted the "5", "9", "5" of your original string. The Python join() method is a string method, and takes a list of things to join with the string. A simpler example might help explain:

我已经突出显示了原始字符串的“5”、“9”和“5”。Python join()方法是一个字符串方法，并获取与字符串连接的对象列表。一个简单的例子可能有助于解释:

>>> ",".join(["a", "b", "c"])
'a,b,c'

The "," is inserted between each element of the given list. In your case, your "list" is the string representation "595", which is treated as the list ["5", "9", "5"].

在给定列表的每个元素之间插入“，”。在您的例子中，“list”是字符串表示“595”，它被视为列表[“5”、“9”、“5”]。

It appears that you're looking for + instead:

看起来你在寻找+代替:

print array.array('c', random.sample(string.ascii_letters, 20 - len(strid)))
.tostring() + strid

#2

join takes an iterable thing as an argument. Usually it's a list. The problem in your case is that a string is itself iterable, giving out each character in turn. Your code breaks down to this:

join使用可迭代的东西作为参数。通常是一个列表。在您的例子中，问题是字符串本身是可迭代的，依次给出每个字符。你的代码是这样的:

"wlfgALGbXOahekxSs".join("595")

which acts the same as this:

其作用与此相同:

"wlfgALGbXOahekxSs".join(["5", "9", "5"])

and so produces your string:

这样就产生了你的弦

"5wlfgALGbXOahekxSs9wlfgALGbXOahekxSs5"

Strings as iterables is one of the most confusing beginning issues with Python.

作为可迭代的字符串是Python最令人困惑的开始问题之一。

#3

To append a string, just concatenate it with the + sign.

要附加一个字符串，只需将它与+号连接起来。

E.g.

如。

>>> a = "Hello, "
>>> b = "world"
>>> str = a + b
>>> print str
Hello, world

join connects strings together with a separator. The separator is what you place right before the join. E.g.

连接用分隔符连接字符串。分隔符是您在联接之前放置的。如。

>>> "-".join([a,b])
'Hello, -world'

Join takes a list of strings as a parameter.

联接以字符串列表作为参数。

#4

join() is for concatenating all list elements. For concatenating just two strings "+" would make more sense:

join()用于连接所有列表元素。连接两个字符串“+”会更有意义:

strid = repr(595)
print array.array('c', random.sample(string.ascii_letters, 20 - len(strid)))
    .tostring() + strid

#5

To expand a bit more on what others are saying, if you wanted to use join to simply concatenate your two strings, you would do this:

为了进一步扩展其他人的观点，如果您想使用join来简单地连接两个字符串，您可以这样做:

strid = repr(595)
print ''.join([array.array('c', random.sample(string.ascii_letters, 20 - len(strid)))
    .tostring(), strid])

#6

On providing this as input ,

作为输入，

li = ['server=mpilgrim', 'uid=sa', 'database=master', 'pwd=secret']
s = ";".join(li)
print(s)

Python returns this as output :

Python返回如下输出:

'server=mpilgrim;uid=sa;database=master;pwd=secret'

#1

256