Python Strings Explained: Day 7 of Your Coding Journey

Introduction:

Welcome to Day 7 of my Python journey!

Today, I ventured into the realm of String. These concepts are essential.

String Data Types :

(str → string)

. str is a predefined class in python.

. to get the manual of str class,

>>> help ( str )

. how to create object of str class,

obj = str ()

print ( obj , type ( obj ))

obj = str ( "india" )

print ( obj , type ( obj ))

obj = "ithon"

print ( obj , type ( obj ))

obj = 'a'

print ( obj , type ( obj ))

obj = 'abc'

print ( obj , type ( obj ))

obj = '''this is an example of multiline string'''

print ( obj , type ( obj ) )

obj = """welcome to the python class """

print ( obj , type ( obj ))

. Any sequence of characters within either single quotes or double quotes is considered as a String.

. python does not support char data type.

. in python char is also represented as str object.

. tripple quote is used for multiline string.

. anonymus string object is used for comment line also.

. the object having no name is known as anonymus object.

. to get the length of a string object we can apply len () function.

. str object does not support item assignemnt or item deletion.

. we can not modify string object in future.

. string object is immutable object in python.

INDEXING :

. to target a specific char in a string object we can apply index mechanism.

. by using index we can perfrom read operation with string object

. by using index we can not perfrom write / update / delete operation with string object.

. to provide index with string object we have to use subscript operator

strObj [ index ]

. +ve index range 0 to len - 1

. -ve index supported by str object.

. -ve index range -len to -1

OPERATORS

all the operator available in python is not going to supported with str object

. arithmatic

+ concatination

* repetation

. relational

relational operator in a string object works according to ASCI value.

. membership

in

not in

return bool type object ( True / False )

is

is not

s1 = "Hello Sir"

s2 = "Hello Sir"

print ("sir" in s1 )

print ("H" in s1 )

print ("h" in s1 )

print (" " in s1 )

print (s1 is s2)

s3 = "Hello sir"

print (s1 is s3 )

Example:

arithmatic

obj1 = 'hello '

obj2 = 'sir'

obj = obj1 + obj2

print ( obj )

#obj = obj1 + 10 #TypeError

obj = obj1 + str ( 10 )

print ( obj )

obj = 'hi ' * 3

print ( obj )

relational operator

print ( 'a' < 'b' )

slicing

strObj = 'india'

print ( strObj [ 1 : 4 ] )

print ( strObj [ 1 : 4 : 2 ])

print ( strObj [ : : -1 ])

FUNCTIONS

len ()

max ()

min ()

sum () : can not work with string because string + int is not permitted in python

ord ( ) to get the asci value of a specific char

chr ( ) to get the char from asci value.

str = "Python"

print ("max element =", max(str))

print ("min element =", min(str))

print ("length of list =", len(str))

#print ("sum =", sum (str)) #Error

s= "A"

print ("ASCII value of A=", ord (s))

s1= 90

print ("char of 90=", chr (s1))

Methods :

for change case :

. upper ()

. lower ()

. title ()

. swapcase()

. capitalize()

. split ()

. splitlines ()

. zfill()

.join ()

s = "A$ababc$abcdabcde"

print (s.split ("$"))

print (s.split ("$", 2))

print (s. partition("$",) ) #from left side it will partition

print (s. rpartition("$",) )# from right side it will partition

s1 = '''Heloo c

hello C++

Hello Java

hello Py'''

print (s1)

print (s1.split ("\n"))

print (s1.splitlines ()) #split line wise

s2 = "1"

print (s2)

print (s2.zfill (5)) #zerofill

s3 = "abc"

print (",". join (s3))

print ("==". join (s3))

String Methods :

capitalize() Converts the first character to upper case

casefold() Converts string into lower case

center() Returns a centered string

count() Returns the number of times a specified value occurs in a string

encode() Returns an encoded version of the string

endswith() Returns true if the string ends with the specified value

expandtabs() Sets the tab size of the string

find() Searches the string for a specified value and returns the position of where it was found

format() Formats specified values in a string

format_map() Formats specified values in a string

index() Searches the string for a specified value and returns the position of where it was found

isalnum() Returns True if all characters in the string are alphanumeric

isalpha() Returns True if all characters in the string are in the alphabet

isascii() Returns True if all characters in the string are ascii characters

isdecimal() Returns True if all characters in the string are decimals

isdigit() Returns True if all characters in the string are digits

isidentifier() Returns True if the string is an identifier

islower() Returns True if all characters in the string are lower case

isnumeric() Returns True if all characters in the string are numeric

isprintable() Returns True if all characters in the string are printable

isspace() Returns True if all characters in the string are whitespaces

istitle() Returns True if the string follows the rules of a title

isupper() Returns True if all characters in the string are upper case

join() Converts the elements of an iterable into a string

ljust() Returns a left justified version of the string

lower() Converts a string into lower case

lstrip() Returns a left trim version of the string

maketrans() Returns a translation table to be used in translations

partition() Returns a tuple where the string is parted into three parts

removeprefix() Return a str with the given prefix string removed if present.

removesuffix() Return a str with the given suffix string removed if present.

replace() Returns a string where a specified value is replaced with a specified value

rfind() Searches the string for a specified value and returns the last position of where it was found

rindex() Searches the string for a specified value and returns the last position of where it was found

rjust() Returns a right justified version of the string

rpartition() Returns a tuple where the string is parted into three parts

rsplit() Splits the string at the specified separator, and returns a list

rstrip() Returns a right trim version of the string

split() Splits the string at the specified separator, and returns a list

splitlines() Splits the string at line breaks and returns a list

startswith() Returns true if the string starts with the specified value

strip() Returns a trimmed version of the string

swapcase() Swaps cases, lower case becomes upper case and vice versa

title() Converts the first character of each word to upper case

translate() Returns a translated string

upper() Converts a string into upper case

zfill() Fills the string with a pspecified number of 0 values at the beginning

str = "Python"

print (str)

s1 = str .center (13, "*")

print (s1)

s2= str.rjust (9, "*")

print (s2)

s3= str .ljust (9, "*")

print (s3)

s1= s1.strip ("*")

print (s1)

s2= s2.lstrip ("*")

print (s2)

s3= s3.rstrip ("*")

print (s3)

expandtabs ()

str = "hello sir my name is raj & my dept is ME"

print (str)

print (str.expandtabs (1) )

print (str.expandtabs (0) )

print (str.expandtabs (2) )

count ()

find ()

replace ()

index ()

obj = "litiitniit"

#ind 0123456789

print (obj) #litiitniit

print (obj.count ("i")) #from 0 to len -1 index

print (obj.count ("i", 2 )) # 2 means start index to len -1

print (obj.count ("i", 2 , 4)) # 2 means start index 4 means stop index - 1

print (obj.count ("i", 2 , 5)) # 2 means start index 4 means stop index - 1

print ("---------find method ----------")

print ( obj.find ("i"))

print ( obj.find ("i", 0))

print ( obj.find ("i", 1))

print ( obj.find ("i", 7))

print ( obj.find ("i", 8))

print ( obj.find ("i", 9)) #-1

print ("-----index method -----")

print (obj.index ("i"))

print (obj.index ("i", 0))

print (obj.index ("i", 1))

print (obj.index ("i", 8))

#print (obj.index ("i", 9)) #Error

print (obj)

print (obj.replace ("i", "I") )

print (obj.replace ("i", "I", 2 ) )

print (obj.replace ("i", "I", 4 ) )

format ()

format_map ()

str = "hello sir my name is {name} , my age is {no} & dept is {dept}"

print (str)

print (str.format (name = "raj", no = 23, dept = "cse") )

maketrans ()

translate ()

str= "Hello Python"

table = str.maketrans ("P", "J")

#print (table )

print (str.translate (table) )

Challenges:

1. Understanding String operations.

2. Handling coding errors.

Resources:

1. Official Python Documentation: String

2. Scaler' Python Tutorial: string

Goals for Tomorrow:

1. Explore operator in python.

2. Learn about operator , types.

Conclusion:

Day 7 was a success! String is now under my belt.

What are your favorite Python libraries for data manipulation? Share in the comments below.

Connect with me:

LinkedIn: [ https://www.linkedin.com/in/archana-prusty-4aa0b827a/ ]

GitHub: [ https://github.com/p-archana1 ]

Join the conversation:

Share your own learning experiences or ask questions in the comments.

Next Post:

Day 8: Operators and types.

Happy reading!!

THANK YOU!!