How do I get a substring of a string in Python?

Question

Is there a way to substring a string in Python, to get a new string from the third character to the end of the string?

Maybe like myString[2:end]?

Answer 1

Maybe I missed it, but I couldn't find a complete answer on this page to the original question(s) because variables are not further discussed here. So I had to go on searching.

Since I'm not yet allowed to comment, let me add my conclusion here. I'm sure I was not the only one interested in it when accessing this page:

 >>>myString = 'Hello World'
 >>>end = 5

 >>>myString[2:end]
 'llo'

If you leave the first part, you get

 >>>myString[:end]
 'Hello' 

And if you left the : in the middle as well you got the simplest substring, which would be the 5th character (count starting with 0, so it's the blank in this case):

 >>>myString[end]
 ' '

Answer 2

a="Helloo"
print(a[:-1])

In the above code, [:-1] declares to print from the starting till the maximum limit-1.

OUTPUT :

>>> Hello

Note: Here a [:-1] is also the same as a [0:-1] and a [0:len(a)-1]

a="I Am Siva"
print(a[2:])

OUTPUT:

>>> Am Siva

In the above code a [2:] declares to print a from index 2 till the last element.

Remember that if you set the maximum limit to print a string, as (x) then it will print the string till (x-1) and also remember that the index of a list or string will always start from 0.

Answer 3

I would like to add two points to the discussion:

1. You can use None instead on an empty space to specify "from the start" or "to the end":

   'abcde'[2:None] == 'abcde'[2:] == 'cde'
   

   This is particularly helpful in functions, where you can't provide an empty space as an argument:

   def substring(s, start, end):
       """Remove `start` characters from the beginning and `end` 
       characters from the end of string `s`.
   
       Examples
       --------
       >>> substring('abcde', 0, 3)
       'abc'
       >>> substring('abcde', 1, None)
       'bcde'
       """
       return s[start:end]
   

2. Python has slice objects:

   idx = slice(2, None)
   'abcde'[idx] == 'abcde'[2:] == 'cde'
   

Answer 4

Just for completeness as nobody else has mentioned it. The third parameter to an array slice is a step. So reversing a string is as simple as:

some_string[::-1]

Or selecting alternate characters would be:

"H-e-l-l-o- -W-o-r-l-d"[::2] # outputs "Hello World"

The ability to step forwards and backwards through the string maintains consistency with being able to array slice from the start or end.

Answer 5

You've got it right there except for "end". It's called slice notation. Your example should read:

new_sub_string = myString[2:]

If you leave out the second parameter it is implicitly the end of the string.

Answer 6

Substr() normally (i.e. PHP and Perl) works this way:

s = Substr(s, beginning, LENGTH)

So the parameters are beginning and LENGTH.

But Python's behaviour is different; it expects beginning and one after END (!). This is difficult to spot by beginners. So the correct replacement for Substr(s, beginning, LENGTH) is

s = s[ beginning : beginning + LENGTH]