正则表达式区别+和*

Question

这可能是一个转储问题。但我要问清楚。

我有一条短信

string = ''' t Network Questions
Is there         something like a (readied) charge in 5e?
 Can you use a
  Bonus Action on a       turn'''

文字是故意散乱的。无意间遇到了这个疑惑

print re.sub(r'\s+',' ',string)

 t Network Questions Is there something like a (readied) charge in 5e? Can you use a Bonus Action on     a turn

看看下一条语句。

 print re.sub(r'\s*',' ',string)

 t N e t w o r k Q u e s t i o n s I s t h e r e s o m e t h i n g l i k e a ( r e a d i e d ) c h a r g e i n 5 e ? C a n y o u u s e a B o n u s A c t i o n o n a t u r n

唯一的区别是 * 和 +。那么，0 次或多次出现和 1 0r 多次出现究竟是什么意思。任何人都可以解释为什么当我们使用 *.

时它在单词之间 space

Answer 1

`*` matches an empty string as well.

所以Ne之间有一个空的string.So会被space代替。

Answer 2

*是零次或多次出现，零表示空

+是一个或多个Occurrence，它至少匹配一个

Answer 3

+如何匹配字符串

Is there         something like
  |
 \s #one space

Is there         something like
        |
       \s+ #one or more space 

Is there         something like
         |
        \s+ #one or more space

# And so on untile

Is there         something like
                |
               \s+

**如何匹配字符串

Is there         something like
|
\s* #matches here. Because there is zero occurence of space (Before the character I)

Is there         something like
 |
 \s* # matches here as well and so on in all the characters

     #  Here it doesnt match any character, Rather it matches the postion between I and s as there is zero occurence of \s

正则表达式区别+和*

Regular expression difference + and *

python

regex