String Methods

• Introduction

  The aim of this paper is to help the reader get familiar with the standard functions of strings in Python.

• Functions

1 . .count(): This function returns the count of a specific value inside a string , the value is passed as an argument. Syntax:

    s="aabbzzz"
    character_to_be_counted='z'
    frequency=s.count(character_to_be_counted) #This is the generic syntax
    print(frequency)

• The snippet above prints the number of time "z" appears in the string "s" which is 3

2 . .find() and .index(): The reason I have grouped these two together is because they serve almost the same functionality, both of these functions will return the first index of where a specified value is found , however when they fail to find the value, .index() raises a ValueError exception and .find() returns -1. Syntax:

    s="aabbcc"
    answer=s.find("a")
    answer2=s.index("a")
    print(answer,answer2)

• Both of these functions will return 0 (The first occurrence of "a")

3 . .format(): This function places text inside given string, The user needs to define a placeholder inside the string so the function knows where to place specific values. Syntax:

    text="The price of {fruit} is {price}"
    modified_string=text.format(fruit="mango",price=35")
    print(modified_string)

• The output for the snippet above is The price of mango is 35

• format maps the values to their respective placeholders.

4 . .isalpha(): This function returns a boolean value after checking if all characters in a string are alphabets or not. Syntax:

    text1="Company"
    text2="Company10"
    check_alpha1=text1.isalpha()
    check_alpha2=text2.isalpha()
    print(check_alpha1,check_alpha2)

• The above snippet prints True and False respectively.

5 . .replace: This function replaces a given character or a phrase with another one. An optional argument can be added , specifying the number of existing phrases the user wants to remove. Syntax:

    text="I like Bananas"
    current_phrase="Bananas"
    new_phrase="Oranges"
    modified_text=text.replace(current_phrase,new_phrase) #This is the generic syntax
    print(modified_text)

6 . .upper() and .lower(): Both of these functions have similar functionality, .upper() changes all characters in a string to uppercase and .lower() changes all the characters to lowercase. Syntax:

    text="AaAbC"
    upper_text=text.upper()
    lower_text=text.lower()
    print(upper_text,lower_text)

• The snippet above prints AAABC and aaabc respectively.

7 . .split(): This function splits the string on the basis of the given argument which is space by default. Syntax:

    text1="This is a sentence"
    new_list=text1.split()
    print(new_list)

• The above snippet will print ["This","is","a","sentence"] splitting the above string by space

8 . .strip(): This function removes the leading and trailing occurrences of a specified string, the default argument is space. Syntax:

    text1="  abcd    "
    new_text1=text1.strip()
    print(new_text1)

• The above snippet will print abcd removing all instances of spaces from the right and the left end.

9 . .join(): This function is the polar opposite of the .split() function , This function will help you out if you want to join a list to make a string based on a separator. Syntax:

    list=["This","is","a","sentence"]
    separator="  "
    answer=separator.join(list)
    print(answer)

• The snippet above will print This is a sentence creating a space will adding the specified separator between the words.

10 . isdigit(): Returns True if all characters in the given string are digits , else returns False. Syntax:

    digit="10273"
    non_digit="adefre13"
    print(digit.isdigit())
    print(non_digit.isdigit())

• The snippet above prints True and False respectively.