How to get char from string by index?

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Question :

How to get char from string by index?

Lets say I have a string that consists of x unknown chars. How could I get char nr. 13 or char nr. x-14?

Asked By: TheBW


Answer #1:

First make sure the required number is a valid index for the string from beginning or end , then you can simply use array subscript notation.
use len(s) to get string length

>>> s = "python"
>>> s[3]
>>> s[6]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: string index out of range
>>> s[0]
>>> s[-1]
>>> s[-6]
>>> s[-7]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: string index out of range
Answered By: DhruvPathak

Answer #2:

In [1]: x = "anmxcjkwnekmjkldm!^%@(*)#_+@78935014712jksdfs"
In [2]: len(x)
Out[2]: 45

Now, For positive index ranges for x is from 0 to 44 (i.e. length – 1)

In [3]: x[0]
Out[3]: 'a'
In [4]: x[45]
IndexError                                Traceback (most recent call last)

/home/<ipython console> in <module>()

IndexError: string index out of range

In [5]: x[44]
Out[5]: 's'

For Negative index, index ranges from -1 to -45

In [6]: x[-1]
Out[6]: 's'
In [7]: x[-45]
Out[7]: 'a

For negative index, negative [length -1] i.e. the last valid value of positive index will give second list element as the list is read in reverse order,

In [8]: x[-44]
Out[8]: 'n'

Other, index’s examples,

In [9]: x[1]
Out[9]: 'n'
In [10]: x[-9]
Out[10]: '7'
Answered By: avasal

Answer #3:

Previous answers cover about ASCII character at a certain index.

It is a little bit troublesome to get a Unicode character at a certain index in Python 2.

E.g., with s = '????????' which is <type 'str'>,

__getitem__, e.g., s[i] , does not lead you to where you desire. It will spit out semething like ?. (Many Unicode characters are more than 1 byte but __getitem__ in Python 2 is incremented by 1 byte.)

In this Python 2 case, you can solve the problem by decoding:

s = '????????'
s = s.decode('utf-8')
for i in range(len(s)):
    print s[i]
Answered By: ghchoi

Answer #4: has an excellent section on strings here. Scroll down to where it says “slice notation”.

Answered By: Joel Cornett

Answer #5:

Another recommended exersice for understanding lists and indexes:

L = ['a', 'b', 'c']
for index, item in enumerate(L):
    print index + 'n' + item

Answered By: Droogans

Answer #6:

This should further clarify the points:

a = int(raw_input('Enter the index'))
str1 = 'Example'
leng = len(str1)
if (a < (len-1)) and (a > (-len)):
    print str1[a]
    print('Index overflow')

Input 3
Output m

Input -3
Output p

Answered By: Arnab Ghosal

Answer #7:

I think this is more clear than describing it in words

s = 'python'
print(s[len(s) - 1])

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