Detailed description of Strings in Python

Like many other popular
programming languages, strings in
Python are arrays of bytes representing
Unicode characters. However, Python does
not have a character data type, a single
character is simply a string with a length of
1. Square brackets can be used to access
elements of the string.
STRINGS

How to change or delete a string?

Strings are immutable. This
means that elements of a string cannot be
changed once it has been assigned. We can
simply reassign different strings to the
same name.
>>> my_string = 'programiz'
>>> my_string[5] = 'a'
TypeError: 'str' object does not support
item assignment.
How to change or delete a string?

How to create a string in Python?

How to create a string in Python?
Strings can be created by enclosing
characters inside a single quote or double
quotes. Even triple quotes can be used in
Python but generally used to represent
multiline strings and docstrings.
STRINGS

REPRESENTATION OF STRING
>>> s = “Hello Python”
This is how Python would index the string:
Forward Indexing
Backward Indexing

STRINGS – Programming Example

STRINGS - Example
Output Next Slide...

How to access characters in a string?

We can access individual characters
using indexing and a range of characters
using slicing. Index starts from 0. Trying to
access a character out of index range will
raise an IndexError. The index must be an
integer. We can't use float or other types,
this will result into TypeError.
STRINGS

Python allows negative indexing for
its sequences.
The index of -1 refers to the last item,
-2 to the second last item and so on. We
can access a range of items in a string by
using the slicing operator (colon).
STRINGS

SLICING STRINGS EXAMPLES
For example:
>>>“Program”[3:5]
will result in:
‘gr ’
>>>“Program”[3:6]
will yield:
‘gra’
>>>p = “Program”
>>>p [:4]
‘Prog’
>>>p [4:]
‘ram’
>>>p [3:6]
‘gra’

More Functionality of String
>>> len(“Sainik School”)
13
>>>print(“Sainik” + “School”)
Sainik School
>>>print(“A” * 4 )
AAAA
>>>”sa” in “sainik”
True
>>>”pr” in “computer”
False
Finding Length of string
String Concatenation
String Repeat
Substring Tests

More Functionality of String
>>> name1="computer"
>>> name2=name1[3:5]
>>>name2
pu String Slicing

String Methods
In Python, a method is a function that is
defined with respect to a particular object.
Syntax:
object.method(arguments)
For Example:
>>>name=“Classic”
>>>name.find(“s”)
3
the first position
where “s” appears
String object String Method Method Argument

1. capitalize() Method
Capitalizes first letter of string
First letter capitalization

2. lstrip() & 3. rstrip() Methods
lstrip() method is used to remove left
padded spaces in a given string
>>>name1=“ a “
>>>name1.lstrip()
‘a ‘
rstrip() method is used to remove right
padded spaces in a given string
>>>name1.rstrip()
‘ a’
Removing left spaces
Removing right spaces

4. strip() Method
strip() method is used to remove left
and right padded spaces in a given string
>>>name1=“ a “
>>>name1.strip()
‘a‘
Removing left and right spaces for a given string

5. lower() Method
lower() method is used to convert
given string in to lower case.
>>>name1=“ SAINIK “
>>>name1.lower()
sainik
Converting in to lower case

6. upper() Method
upper() method is used to convert
given string in to upper case.
>>>name1=“ sainik “
>>>name1.upper()
SAINIK
Converting in to upper case

7. title() Method
title() method is used to convert given
string in to title case. Every first chatacter of
word of a given string is converted to title
case.
>>>name1=“ praveen murigeppa jigajinni“
>>>name1.title()
Praveen Murigeppa Jigajinni
In every word first letter is capitalized

8. swapcase() Method
swapcase() method is toggle the case.
Meaining upper to lower and lower to upper
case.
>>>name1=“ PrAvEeN“
>>>name1.swapcase()
pRaVeEn
Every character case is changed

9. ljust() Method
ljust() method is used to add spaces to
the left side of the given string
>>>name1=“ Jigajinni“
>>>name1.ljust(15)
‘Jigajinni ’
Left side padded with spaces
Note: string length is 9 and 6 spaces
added to the left side of string

10. rjust() Method
rjust() method is used to add spaces to
the right side of the given string
>>>name1=“ Jigajinni“
>>>name1.rjust(15)
‘ Jigajinni’
Right side padded with spaces
Note: string length is 9 and 6 spaces
added to the right side of string

11. center(width, fillchar) Method
The method center() returns centered
in a string of length width. Padding is done
using the specified fillchar. Default filler is a
space.
Centered string

12. zfill() Method
zfill() method is used to fill the zero to
a given string
>>>name1=“ 123“
>>>name1.zfill(15)
‘00123 ’
Filling Zeros

13. find() Method
find() method is used to find a
perticular character or string in a given
string.
>>> name1="praveen"
>>> name1.find("e")
4
e is present at 4th location (first appearance)
in a given string

14. count() Method
count() method is used to the number
of times character or string appears in a
given string.
>>>name1=“praveen“
>>>name1.count(“e”)
2
2 times e appears in a given string

15. stratswith() Method
startswith() method is used check
string start with particular string or not
>>>name1.startswith(“a”)
False
Given string not starting with “a”

16. endswith() Method
endswith() method is used check string
ends with particular string or not
>>>name1.endswith(“en”)
True
Given string ends with “en”

17. isdigit() Method
isdigit() method is used check string is
digit (number) or not and returns Boolean
value true or false.
>>>name2=“123”
>>>name2.isdigit()
True
>>name1=“123keyboard“
>>name1.isdigit()
False
Given string not number so false
Given string is
number

18. isnumeric() Method
isnumeric() is similar to isdigit()
method and is used check string is digit
(number) or not and returns Boolean value
true or false.
>>>name2=“123”
>>>name2.isnumeric()
True
>>name1.isnumeric()
False
Given string is
number

19. isdecimal() Method
isnumeric(),isdigit() and isdecimal()
methods are used to check string is digit
(number) or not and returns Boolean value
true or false.
>>>name2=“123”
>>>name2.decimal()
True
>>name1.isnumeric()
False
Given string is
number

20. isalpha() Method
isalpha() method is used check string is
digit or not and returns Boolean value true or
false.
>>>name2=“123”
>>>name2.isalpha()
False
>>name1=“123computer“
>>name1.isalpha()
False
>>>name3=“Keynoard”
>>>Name3.isaplpha()
True
Given string not
string it contains
digits
Given string does
not contain string
It’s a string

21. isalnum() Method
isalnum() method is used check string is
alpha numeric string or not.
>>>name2=“123”
>>>name2.isalnum()
True
>>>name1=“123computer“
>>>name1.isalnum()
True
>>>name3=“Praveen”
>>>name3.isalnum()
True
Given string is
alpha numeric

22. islower() Method
islower() method is used check string
contains all lower case letters or not, it returns
true or false result.
>>>name2.islower()
False
>>>name1.islower()
True
Given string is not
lower case string
Given string is
lower case string

23. isupper() Method
isupper() method is used check string
contains all letters upper case or not, it returns
true or false result.
>>>name2.isupper()
False
>>>name1=“PRAVEEN“
>>>name1.isupper()
True
Given string is not
upper case string
Given string is
upper case string

24. isspace() Method
isspace() method is used check string
contains space only or not.
>>>name2=“ ”
>>>name2.isspace()
True
>>>name1=“PRAVEEN M J“
>>>name1.isspace()
False
Given string
contains space only
Given string not
containing space only

25. find() Methods
find() method is used to find a
particular string (substring) in a given
string.
>>>name=“Classic”
>>>name.find(“s”)
3
the first position
where “s” appears
String object String Method Method Argument

26. str() Method
str() method is used convert non
string data into string type.
>>>str(576)
‘576’
576 is number converted to string

27 len() Method
len() method is used get a length of
string.
>>>len(“Praveen”)
7
Gives the string length

28 max() Method
max() method is used get a max
alphabet of string.
>>>max(“Praveen”)
v
Gives max character

29 min() Method
min() method is used get a max
alphabet of string.
>>>min(“Praveen”)
P
Gives min character P because it has
ASCII Value 65

30 split() Method
split() method is used split a string.
Split in to several words or substrings

30 split() Method
split() method is used split a string
according to delimiter.
Split in to several words or substrings
according to delimiter

31 index() Method
Same as find(), but raises an
exception if str not found.
>>> name="Sainik“
>>> name.index("a",3,5)
ValueError: substring not found
>>> name.index("a",1,5)
1 Value error
Character found, returning the position

32. ord() Method
ord() method is used get a ASCII
value for a character.
>>ord(“a”)
97
97 is the ASCII value for character ‘a’

33. chr() Method
char() method is used get a
character for an ASCII value.
>>chr(97)
‘a’
‘a’ ASCII value is 97

Detailed description of Strings in Python

Detailed description of Strings in Python

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