Python Strings Operations and Methods

String Operations

Concatenation of Two or More Strings

  • Joining of two or more strings into a single one is called concatenation.
  • The + operator does this in Python. Simply writing two string literals together also concatenates them.
  • The * operator can be used to repeat the string for a given number of times.
  • #Sample Code
    s1 = "Hello "
    s2 = "Anand "
    
    #concatenation of 2 strings
    print(s1 + s2)
    
    #repeat string n times
    print(s2 * 3)
    
    Output:
    Hello Anand 
    Anand Anand Anand 
    

    ord() and chr() Functions

    # ord() – function returns the ASCII code of the character.
    ch = 'b'
    print(ord(ch))
    
    Output:
    98
    
    # chr() – function returns character represented by a ASCII number.
    print(chr(97))
    print(chr(65))
    print(chr(98))
    
    Output:
    a
    A
    b
    

    String Comparison

  • You can use ( > , < , <= , >= , == , != ) to compare two strings.
  • Python compares string lexicographically i.e using ASCII value of the characters.
  • #Sample Code for String Comparison 
    
    print("Python" == "Python")
    print("PYTHON" == "Python")
    
    print("PYTHON" != "Java")
    
    print("Python" > "PYTHON")
    print("Python" < "PYTHON")
    
    print("Python" >= "PYTHON")
    print("Python" <= "PYTHON")
    
    Output:
    True
    False
    True
    True
    False
    True
    False
    

    String Membership Operator

    # Sample Code for 'in' operator
    Str1 = "All the best"
    print('best' in Str1)
    
    # Sample Code for 'not in' operator
    str2 = "Happy Learning"
    print('sad' not in str2)
    
    Output:
    True
    True
    

    Iterating String using for loop

    # Program to print each character of a string
    for x in "python":
        print(x)   
        
    Output:
    p
    y
    t
    h
    o
    n
    

    String Functions or Methods

    1. strip() method removes any whitespace from the beginning or the end

    str1 = "    Welcome to Python Session "
    print(str1) # Printing with Space
    print(str1.strip()) # Printing without Space 
    
    Output:
        Welcome to Python Session 
    Welcome to Python Session
    

    2. len() method returns the length of a string

    str2 = "Python String Length"
    print('Length of String is ',len(str2))
    
    Output:
    Length of String is  20
    

    3. lower() method returns the string in lower case

    str3 = "WELCOME"
    print(str3.lower())  
    
    Output:
    welcome
    

    4. islower() method check whether string is in lower case of not.

    str4 = "welcome"
    print(str4.islower())
    
    Output:
    True
    

    5. upper() method returns the string in upper case

    str5 = "welcome"
    print(str5.upper())
    
    Output:
    WELCOME
    

    6. isUpper() method check whether string is in upper case of not.

    str6 = "WELCOME"
    print(str6.isupper())
    
    Output:
    True
    

    7. isalpha() method check Checks if All Characters are Alphabets

    str9 = "Python"
    str10 = "Python123"
    str11 = "123"
    str12 = "Python123@#@#"
    print(str9.isalpha())
    print(str10.isalpha())
    print(str11.isalpha())
    print(str12.isalpha())  
    
    Output:
    True
    False
    False
    False
    

    8. isdigit() method check whether string is Checks Digit Characters

    str9 = "Python"
    str10 = "Python123"
    str11 = "123"
    str12 = "Python123@#@#"
    print(str9.isdigit())
    print(str10.isdigit())
    print(str11.isdigit())
    print(str12.isdigit())
    
    Output:
    False
    False
    True
    False
    

    9. isalnum() method check whether string is Checks Alphanumeric Character

    str9 = "Python"
    str10 = "Python123"
    str11 = "123"
    str12 = "Python123@#@#"
    print(str9.isalnum())
    print(str10.isalnum())
    print(str11.isalnum())
    print(str12.isalnum())
    
    Output:
    True
    True
    True
    False
    

    10. count() method returns the number of occurrences of a substring in the given string.

    string = "Python is easy to learn.This"
    string = "Python is easy to learn. This is also called as easy programming language"
    substring = "is"
    
    count = string.count(substring)
    
    # print count
    print("The count is:", count)
    
    Output:
    The count is: 2
    

    11. join() method returns a string concatenated with the elements of an iterable.

    string1 = '-'
    string2 = '123456'
    
    print('string1.join(string2):', string1.join(string2))
    
    Output:
    string1.join(string2): 1-2-3-4-5-6
    

    12. split() method breaks up a string at the specified separator and returns a list of strings.

    # splits at space
    str1= 'Welcome to Python Class'
    print(str1.split())
    
    # splits at ','
    str2 = "Vinoth,Anand,Santhosh,Raghul"
    # splits at ','
    print(str2.split(','))
    
    # splits at ':'
    str3 = "121212121:1212121:21434322434:4234234"
    print(str3.split(':'))
    
    Output:
    ['Welcome', 'to', 'Python', 'Class']
    ['Vinoth', 'Anand', 'Santhosh', 'Raghul']
    ['121212121', '1212121', '21434322434', '4234234']
    

    13. find() method returns the index of first occurrence of the substring (if found). '
    If not found, it returns -1.

    str = 'Do you like programming?'
    print("Substring 'like' at index':", str.find('like'))
    
    Output:
    Substring 'like' at index': 7
    

    14. replace() method returns a copy of the string where all occurrences of a substring is replaced with another substring.

    # Character replacement
    fruit = 'Appla'
    print (fruit.replace('a', 'e'))
    
    # String replacement
    color = 'red, rose, greeen , yellow, rose'
    print (color.replace('rose', 'blue'))
    
    # The original string is unchanged
    print ('Original string:', fruit)
    print ('Replaced string:', fruit.replace('a', 'e'))
    
    Output:
    Apple
    red, blue, greeen , yellow, blue
    Original string: Appla
    Replaced string: Apple
    

    15. sorted() method returns a sorted list from the given iterable.

    String = 'dzsewkitng'
    print(sorted(String))
    
    Output:
    ['d', 'e', 'g', 'i', 'k', 'n', 's', 't', 'w', 'z']
    

    16. startswith() method returns True if a string starts with the specified prefix.
    If not, it returns False.

    text = "Python is easy to learn"
    print(text.startswith("Python"))
    
    Output:
    True
    

    17. endswith() method returns True if a string ends with the specified suffix.
    If not, it returns False.

    text = "Python is easy to learn"
    print(text.endswith("learn"))
    
    Output:
    True
    
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