PYTHON

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Practicals

Python Theory

Strings:

  • Strings is a sequence of characters.
  • Strings may contain alphabets, numbers and special characters.
  • Usually strings are enclosed with single quotes or double quotes.
  • Strings are immutable in nature.
    • Example
    # Defining strings in Python

    string = 'skillpundit'
    print(string)

    string1 = "skillpundit"
    print(string1)

    string2 = '''skillpundit'''
    print(string2)

    # triple quotes string can extend multiple lines
    string3 = """HI, welcome to skillpundit"""
    print(string3)
    Output
    SkillPundit: Python-Strings-Declaration

    String Indexing:

  • Indexes are locations for specific characters in string.

    • String Slicing:

  • Slicing operation is used to return/select/slice particular substring based on requirements.
  • A segment of string is called Slice.

    • HELLO
    01234
    -5-4-3-2-1

    Syntax
    string _variablename [start:end]
    Example
    #Accessing string characters in Python
    str = 'skillpundit'
    print('str = ', str)

    #frist character
    print('str [0] =', str[0])

    #last character
    print('str [-1] =', str[-1])

    #slicing 2nd to 5th character
    print('str [1:5] =', str[1:5])

    #slicing 5th to 2nd last character
    print('str [4:-2] =', str[5:-2])

    print('str [0:15:2 ] =', str[0:11:2])
    Output
    SkillPundit: Python-String-Slicing

    Strings Concatenation:

  • Joining the two or more strings into a one string is called concatenation.
  • The ‘+’ operator used for string concatenation.
    • Example
    #Python String Operations
    str1 = ' welcome to '
    str2 = 'skillpundit'

    # using +
    print('str1 + str2 = ', str1 +"" +str2)

    # using *
    print('str2 * 2 = ', str2 * 2)
    Output
    SkillPundit: Python-String-Concatenation

    Strings Functions and Methods:

    len()min() max() isalnum() isalpha()
    isdigit() islower()isupper() isspace()isidentifier()
    endswitch() startswitch()find() count() capitalize()
    title()lower() upper()swapcase()replace()
    center()ljust()rjust()center()isstrip()
    rstrip()strip()   

    1. Converting string functions:

    capitalize()Only the first character capitalized.
    lower() All characters converted to lowercase.
    upper() All characters converted to uppercase.
    title()First character capitalized in each word.
    swapcase()Lower case letters are converted to uppercase and uppercase letters are converted to lowercase.
    replace(old,new)Replaces old string with new string.
    Example
    #string functions
    str = "welcome to skillpundit"
    print("Capitalize:", str.capitalize())
    print("Lowercase:", str.lower())
    print("Uppercase:", str.upper())
    print("Titlecase", str.title())
    print("Swapcase:", str.swapcase())
    print("Replacecase:", str.replace("skillpundit","python"))
    Output
    SkillPundit: Python-String-Functions

    2. Formatting string functions:

    center(width)Returns a string centered in a field of given width.
    ljust(width) Returns a string left justified in a field of given width.
    rjust(width) Returns a string right justified in a field of given width.
    format(items)Format a string.
    Example
    #Formatting string Functions:

    a = input("Enter String:")

    print("Center Alignment:", a.center(20))
    print("Left Alignment:", a.ljust(20))
    print("Right Alignment:", a.rjust(20))
    Output
    SkillPundit: Python-Strings-Formatting

    3. Removing whitespace Characters:

    lstrip()Returns a string with leading and trailing whitespace characters removed.
    rstip Returns a string with whitespace characters removed.
    strip() Returns a string with trailing whitespace characters removed.

    4. String Modules :

  • String module contains a number of functions to process standard Python strings.
    • Mostly used string modules:
    • string.upper()
    • string.lower()
    • string.split()
    • string.join()
    • string.replace()
    • string.count()
    • string.find()
    Example
    a = 'skillpundit'
    b = a.capitalize()
    print(b)

    b = a.count('i')
    print(b)

    b = a.find('u')
    print(b)

    b = a.index('d')
    print(b)

    b = a.isalnum( )
    print(b)

    b = a.lower( )
    print(b)

    b = a.upper( )
    print(b)
    b = a.strip( )
    print(b)
    Output
    SkillPundit: Python-Strings-Modules

    Strings are Immutable:

  • Strings are immutable character sets.
  • Once a string is generated, you cannot change any character within the string.
    • Example
    a = 'python program'

    print(a[0])
    print(a[8])

    a [0]= "b"
    Output
    SkillPundit: Python-Strings-Immutable