• A string is nothing but a series of characters. 

• Anything inside quotes is considered a string in Python, and you can use single (‘’) or double quotes (“”) around your strings like this:
      “Hello String”
        ‘Hello String’

• This flexibility will help us to use quotes and apostrophes within our strings:
  “I love ‘Python’ ”
  ‘I said, “I love Python”’

- concatenate  String using , and +  

 # using ','(Used with all type)
    print(a,"concatenated with",b)

  #using '+' (Only using with String)
    print(a+" concated with "+b)

- Adding Whitespace to Strings with Tabs or Newlines                      
    print(“I am good at \n \tC\n\tJava\n\t.Net”) #\n used to start tying from new line and \t used to add space

-  String Function.
a = “ python is my world ”  #a is a string
    title() - where each word begins with a capital letter. (a.title())

    upper() - string to all uppercase (a.upper())

    lower() - string to all lowercase(a.lower())

    strip() - remove whitespaces(a.trip())

    lstrip() - strip whitespace from the left side of a string (a.lstrip())

    rstrip() - strip whitespace from the right side of a string(a.rstrip())

    str() -    convert the numerical value to string(str())

capitalize(),title(),upper(),lower(),casefold(),swapcase

1. capitalize()

• it only capitalize first character of the first word from the given string.

• if the 1st character is number of the first word then this method doestn't capitalize second character

2. title()

• it capitalize first character of every word from the given string.

• if the 1st character is number from any word in the string it will capitalize 2nd character.

str = "i am using python"

print(str.capitalize()) #I am using python

print(str.title()) #I Am Using Python

str = "i am using 'python'"

print(str.capitalize()) #I am using 'python'

print(str.title()) #I Am Using 'Python'

str = "i want 5g"

print(str.capitalize()) #I want 5g

print(str.title()) #I Want 5G

str = "5g"

print(str.capitalize()) #5g

print(str.title()) #5G’

3. casefold()

4. lower()

• used to convert a given string into lowercase.

str = "ß" #germanword

print(str.casefold()) #ss

print(str.lower()) #ß

str1 = "ss"

print(str.casefold() == str1.casefold()) #ss

print(str.lower() == str1.lower()) #ß

str = "I am Suraj"

print(str.lower())#i am suraj

5. upper()

• used to convert a given string into upper case.

print(str.upper())#I AM SURAJ

6. swapcase()

• converts all uppercase characters to lowercase and all lowercase characters to uppercase characters of the given string, and returns it.

print(str.swapcase())#i AM sURAJ

7. centre()

• given string padded with specified character.

• If you don't provide a specified character. It will take whitespace.

centre(width,char) #char is optional

    str = "banahhh"

print(str.center(60,"*"))#if the space not contains in the given string then this method added extra char (i.t '*') at right side of the string

str = "ban ahhh"

print(str.center(60,"*"))#if the space contains in the given string then this method added extra char (i.t '*') at left side of the string

str = "banahhh"

print(str.center(60))

8. count()

• return number of occurrence of a substring from given string

• case sensitive  "i" and "I" is different

• count(string,startIndex,endIndex) #startIndex,endIndex are optional

str = "I like sandwich, I like pizza"

subString = "I"

print("Substring count for {} is {}".format(subString,str.count(subString)))

str = "I like sandwich, I like pizza"

subString = "i"

print("Substring count for {} is {}".format(subString,str.count(subString)))

str = "I like sandwich, I like pizza"

subString = "lik"

print("Substring count for {} is {}".format(subString,str.count(subString)))

str = "I like sandwich, I like pizza"

subString = "sand "

print("Substring count for {} is {}".format(subString,str.count(subString)))

str = "I like sandwich, I like pizza"

subString = "i"

print("Substring count for {} is {}".format(subString,str.count(subString,3,28)))

str = "I like sandwich, I like pizza"

subString = "i"

print("Substring count for {} is {}".format(subString,str.count(subString,4,28)))

str = "I like sandwich, I like pizza"

subString = "i"

print("Substring count for {} is {}".format(subString,str.count(subString,400,288)))

9. endswith()

• return true if  the given string end with specified suffix otherwise return false

• In suffix we provide string or tuple.

• endswith(suffix,startindex,endindex)#startIndex,endIndex are optional

       print(str.endswith("za"))#True

       print(str.endswith(("za","ch","ke"),7,15))#True

10.  startswith()

• return true if  the given string end with specified prefix otherwise return false

• In prefix we provide string or tuple.

• startswith(prefix,startindex,endindex)#startIndex,endIndex are optional

                      print(str.startswith("sa"))#False

                      print(str.startswith(("sa","ch","ke"),7,15))#True

11.  expandtabs() 

•  All tab characters '\t' replaced with whitespace characters until the next multiple of tabsize parameter.

• extpandtabs(tabsize) //tabsize is optional by default it is 8

• 8,16,24,32,40..

• All\tT At the time of count \t position count prevoius \t == number of spaces added in prevoius \t

str = "All\tWe are good\tIn\tPython"

print(str.expandtabs())

print(len(str.expandtabs()))#"All     We are good     In      Python"

print(len("All     We are good     In      Python"))

print(str.expandtabs(3))#All we are good   In Python

print(len(str.expandtabs(3)))

print(len("All we are good   In Python"))

12. encode()

• returns the encoded version of the given string.

• Since Python 3.0, strings are stored as Unicode, i.e. each character in the string is represented by a code point. So, each string is just a sequence of Unicode code points.

• For efficient storage of these strings, the sequence of code points is converted into a set of bytes. The process is known as encoding.

• encode(encoding='UTF-8',errors='strict') #encoding and errors are optional

                               print(str.encode(encoding='UTF-8',errors='strict'))

                         print(str.encode())

13. find()

• returns the index of first occurrence of the substring (if found). If not found, it returns -1

• find(str,sInd,eInd) #sInd,eInd are optional

                if str.find("are") != -1:

     print("substring is found")

else:

     print("substring not found")

if str.find("on") != -1: #how to found check this one found accurate word

     print("substring is found")

else:

     print("substring not found")

if str.find("on",1,0) != -1: #how to found check this one found accurate word

     print("substring is found")

else:

     print("substring not found")

14. strip()

• This method returns the string by removing both the leading and the trailing characters that are given as an input.

• strip([char])#[char] is optional by default it will take whitespace( ) And remove all leading and trailing whitespaces.

                    str = "   Hello I am Chaitanya   "
                        print(str.strip())
                      #Q what will be the output for below two stmt
                     
                      print(str.strip("ya"))
                      print(str.strip(" ya"))#bcuz not have whitespace. try with some other character 8,9    at starting position
                      str = "I am chaitanya"
                      print(str.strip("i"))
                      print(str.strip("I")) #py is case sensitive

15. lstrip()

• This method returns the string by removing the leading characters that are given as an input.

• lstrip([char])#[char] is optional by default it will take whitespace( ) And remove all leading whitespaces.

16. rstrip()

• This method returns the string by removing the trailing characters that are given as an input.

• rstrip([char])#[char] is optional by default it will take whitespace( ) And remove all trailing whitespaces.

17. isalpha()

• This method return true if all character in a string are alphabets otherwise return false.

• In alphabet includes a-z and A-Z

• What if some other languages character are coming like french,marathi,telugu,hindi,tamil

• isalpha()

str = "Chaitanya"

print(str.isalpha())

str = "My name is Chaitanya"

print(str.isalpha())

str = "ā"

print(str.isalpha())

str = "आना"

print(str.isalpha())

18. isalnum()

  #This method return true if all character in a string are alphanumric otherwise return false.

  #In alphabet includes a-z and A-Z and number includes 0-9

  #What if some other languages character are coming like french,marathi,telugu,hindi,tamil

  #isalnum()

str = "Chaitanya07"

print(str.isalnum())

str = "-1"

print(str.isalnum())

str = "ā"

print(str.isalnum())

str = "आना"

print(str.isalnum())

19. isdecimal()

 #This method returns True if all characters in a string are decimal. If not, it returns False.

#isdecimal()

str = "123"

print(str.isdecimal())

str = "0x123"

print(str.isdecimal())

str = "१२"

print(str.isdecimal())

20. isdigit()

 #This method returns True if all characters in a string are degit. If not, it returns False.

 #isdigit()

str = "123"

print(str.isdigit())

str = "-123"

print(str.isdigit())

str = "१२"

print(str.isdigit())

str = "0"

print(str.isdigit())

21. isidentifier()

  #This method returns True if the string is a valid identifier otherwise It returns False.

  #isidentifier()

str = "0"

print(str.isidentifier())

str = "asr"

print(str.isidentifier())

str = "#asr"

print(str.isidentifier())

str = "_asr"

print(str.isidentifier())

22. islower()

#This method returns True if all characters in a string are lower case. If not, it returns False.

#islower()

str = "aAA"

print(str.islower())

str = "asr"

print(str.islower())

23. isupper()

#This method returns True if all characters in a string are upper case. If not, it returns False.

#isupper()

str = "ASDE"

print(str.isupper())

str = "aSr"

print(str.isupper())

24. isnumeric()

#This method returns True if all characters in a string are numeric. If not, it returns False.

#You can write the digit and numeric characters using unicode in the program. For example:

# s = '½'

s = '\u00BD'

#isnumeric()

str = "343"

print(str.isnumeric())

print(s.isnumeric())

s = '\u00AA'

print(s.isnumeric())

s = 'SS12'

print(s.isnumeric())

I will explain the difference with an example:

Suppose you have a string, str1 = 'a b 2w' and you want to capitalize all the first characters but if the first character is a digit then you do not want to change. Desired output -> A B 2w

If you do str1.title() it will result in this -> A B 2W and str1.capitalize() will give the following result -> A b 2w

To get the desired result, you have to do something like this:

for x in str1.split():

str1 = str1.replace(x, x.capitalize())