Traceback (most recent call last):
\n
\u00a0\u00a0<\/b>File “<pyshell#65>”, line 1, in <module>
\n\u00a0\u00a0\u00a0\u00a0<\/b>text[21]
\nIndexError: string index out of range<\/div>\n2. Negative Indexing in Python<\/h4>\n
Negative indexing allows you to access characters in a string from right to left. In this system, the index -1 refers to the last character of the string, -2 refers to the second last, and so on. This feature is particularly useful for quickly accessing the end of a string without needing to know its length. For example, in the string “Python”, the index -1 would return ‘n’ and the index -2 would return ‘o’. Negative indexing provides a convenient way to work with elements at the end of a sequence efficiently.<\/p>\n
To get the letter \u2018b\u2019, we will use the -13 index.<\/p>\n
>>>text[-13]<\/pre>\nOutput:<\/strong><\/p>\n\u2018b\u2019<\/div>\n
Slicing Strings in Python<\/h3>\n
We can get parts<\/strong> of strings at one time by slicing it with the slicing operator [:]<\/strong>.<\/p>\nLet us see how to do this.<\/p>\n
>>> text[2:7]<\/pre>\nOutput:<\/strong><\/p>\n‘ushi ‘<\/div>\n
[2:7]<\/strong> is a slice<\/strong> that gives us the characters from index 2<\/strong> to index 6<\/strong>, index 7<\/strong> is not included<\/strong>.<\/p>\nThe following are different slices for this string:<\/p>\n
>>> text[:] #complete string\r\n'Ayushi bought a pen!'\r\n>>> text[:7] #beginning to index 6\r\n'Ayushi '\r\n>>> text[3:] #index 3 to end\r\n'shi bought a pen!'\r\n>>> text[-2:-7] #-2 to -7 left to right is nothing\r\n''\r\n>>> text[-7:-2] #index -7 to -1 left to right\r\n' a pe'<\/pre>\nWe can also include the number of steps<\/strong> it should take while traversing.<\/p>\n>>> text[::2]\r\n'Auh ogtapn'\r\n>>> text[2:13:2]\r\n'uh ogt'<\/pre>\nIn the above Python strings examples, it skips<\/strong> one character every time.<\/p>\nDeleting\/Updating Strings in Python<\/h3>\n
Strings are immutable<\/strong> and you cannot delete<\/strong> them or update<\/strong> them. You can assign a new object<\/strong> to the variable<\/strong>:<\/p>\n>>> work='RA'\r\n>>> work='SRA'<\/pre>\nThis did not<\/strong> update the string. And you can delete a complete string<\/strong> with the del keyword<\/strong>, but you cannot delete<\/strong> a character<\/strong> or slice<\/strong>.<\/p>\n>>> del work\r\n>>> del text[3]<\/pre>\nOutput:<\/strong><\/p>\nTraceback (most recent call last):
\n
\u00a0\u00a0<\/b>File “<pyshell#25>”, line 1, in <module>
\n\u00a0\u00a0\u00a0\u00a0<\/b>del text[3]
\nTypeError: ‘str’ object doesn’t support item deletion<\/div>\n>>> del text[3:]<\/pre>\nOutput:<\/strong><\/p>\nTraceback (most recent call last):
\n
\u00a0\u00a0<\/b>File “<pyshell#26>”, line 1, in <module>
\n\u00a0\u00a0\u00a0\u00a0<\/b>del text[3:]
\nTypeError: ‘str’ object does not support item deletion<\/div>\nConcatenation and Membership in Python<\/h3>\n1. Concatenation in Python<\/h4>\n
You can join<\/strong> two strings with the + operator<\/strong>. This is called concatenation<\/strong>.<\/p>\n>>> 'come'+' '+'home'<\/pre>\nOutput:<\/strong><\/p>\n‘come home’<\/div>\n
You can also multiply<\/strong> a string by an integer.<\/p>\n>>> 'come'*3<\/pre>\nOutput:<\/strong><\/p>\n‘comecomecome’<\/div>\n
But you cannot concatenate<\/strong> a string with an integer.<\/p>\n>>> 'help'+7<\/pre>\nOutput:<\/strong><\/p>\nTraceback (most recent call last):
\n
\u00a0\u00a0<\/b>File “<pyshell#29>”, line 1, in <module>
\n\u00a0\u00a0\u00a0\u00a0<\/b>‘help’+7
\nTypeError: can only concatenate str (not “int”) to str<\/div>\n2. Membership in Python<\/h4>\n
You can check<\/strong> whether a string is present<\/strong> in another. You can do this with the \u2018in\u2019<\/strong> and \u2018not in\u2019<\/strong> operators.<\/p>\n>>> 'wire' in 'weird'<\/pre>\nOutput:<\/strong><\/p>\nFalse<\/div>\n
>>> 'cool' not in 'honesty'<\/pre>\nOutput:<\/strong><\/p>\nTrue<\/div>\n
Python String Length<\/h3>\n
To calculate the length of a string, you have the len() in-built function<\/strong>.<\/p>\n>>> len(text)<\/pre>\nOutput:<\/strong><\/p>\n20<\/div>\n
You can use this in a for-loop<\/strong> to traverse<\/strong> on a collection<\/strong> or you can use it for some other reasons. Python also has other in-built functions and methods.<\/p>\nWe will talk about them later.<\/p>\n
>>> for index in range(len(text)):\r\n print(index, text[index])<\/pre>\nOutput:<\/strong><\/p>\n0 A
\n1 y
\n2 u
\n3 s
\n4 h
\n5 i
\n6
\n7 b
\n8 o
\n9 u
\n10 g
\n11 h
\n12 t
\n13
\n14 a
\n15
\n16 p
\n17 e
\n18 n
\n19 !<\/div>\n
![\"python](\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/python-string-indexing.jpg\")
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