Strings In Python

What are Strings In Python?

Strings are one of the most fundamental data types in Python, representing sequences of characters. They are used extensively in programming for tasks such as text processing, data manipulation, and user interaction. In this comprehensive guide, we will explore everything you need to know about strings in Python, including basic operations, string methods, formatting, and advanced string manipulation techniques.

In Python, a string is a sequence of characters enclosed within single quotes (‘ ‘), double quotes (” “), or triple quotes (”’ ”’). Strings are used to represent text data or anything that you enclose between single or double quotation marks is considered a string. A string is essentially a sequence or array of textual data.

Strings are used when working with Unicode characters.

Examples:

Here are some basic examples of Python strings:

# Single quotes
name = 'Alice'

# Double quotes
message = "Hello, world!"

# Triple quotes
paragraph = '''Python is a versatile programming language.
It is used for web development, data analysis, artificial intelligence, and more.'''

Example:

name = "Samuel"
print("Hello, " + name)

Output:

Hello, Samuel

Note: It does not matter whether you enclose your strings in single or double quotes, the output remains the same.

Sometimes, the user might need to put quotation marks in between the strings. Example, consider the sentence: He said, “I want to eat an apple”.

How will you print this statement in python?

Wrong way ❌

print("He said, "I want to eat an apple".")

Output:

print("He said, "I want to eat an apple".")
                     ^
SyntaxError: invalid syntax

Right way ✔️

print('He said, "I want to eat an apple".')
#OR
print("He said, \\"I want to eat an apple\\".")

Output:

He said, "I want to eat an apple".
He said, "I want to eat an apple".

What if you want to write multiline strings in python?

Sometimes the programmer might want to include a note, or a set of instructions, or just might want to explain a piece of code. Although this might be done using multiline comments, the programmer may want to display this in the execution of programmer. This is done using multiline strings.

Example:

receipe = """
1. Heat the pan and add oil
2. Crack the egg
3. Add salt in egg and mix well
4. Pour the mixture in pan
5. Fry on medium heat
"""
print(receipe)

note = '''
This is a multiline string
It is used to display multiline message in the program
'''
print(note)

Output:

`1. Heat the pan and add oil 2. Crack the egg 3. Add salt in egg and mix well 4. Pour the mixture in pan 5. Fry on medium heat

This is a multiline string It is used to display multiline message in the program`

Operation on Strings in Python

1. Length of a String in Python

We can find the length of a string using len() function.

Example:

fruit = "Mango"
len1 = len(fruit)
print("Mango is a", len1, "letter word.")

Output:

Mango is a 5 letter word.

2. String as an Array

A string is essentially a sequence of characters also called an array. Thus we can access the elements of this array.

Example:

pie = "ApplePie"
print(pie[:5])
print(pie[6])	#returns character at specified index

Output:

Apple
i

Note: This method of specifying the start and end index to specify a part of a string is called slicing.

Example:

pie = "ApplePie"
print(pie[:5])      #Slicing from Start
print(pie[5:])      #Slicing till End
print(pie[2:6])     #Slicing in between
print(pie[-8:])     #Slicing using negative index

Output:

Apple
Pie
pleP
ApplePie

3. Loop through a String in Python

Strings are arrays and arrays are iterable. Thus we can loop through strings.

Example:

alphabets = "ABCDE"
for i in alphabets:
    print(i)

Output:

A
B
C
D
E

String Methods

Python provides a set of built-in methods that we can use to alter and modify the strings.

1. upper()

The upper() method converts a string to upper case.

Example:

str1 = "AbcDEfghIJ"
print(str1.upper())

Output:

ABCDEFGHIJ

2. lower()

The lower() method converts a string to upper case.

Example:

str1 = "AbcDEfghIJ"
print(str1.lower())

Output:

abcdefghij

3. strip()

The strip() method removes any white spaces before and after the string.

Example:

str2 = " Silver Spoon "
print(str2.strip)

Output:

Silver Spoon

4. rstrip()

the rstrip() removes any trailing characters.

Example:

str3 = "Hello !!!"
print(str3.rstrip("!"))

Output:

Hello

5. replace()

the replace() method replaces a string with another string.

Example:

str2 = "Silver Spoon"
print(str2.replace("Sp", "M"))

Output:

Silver Moon

6. split() :

The split() method splits the give string at the specified instance and returns the separated strings as list items.

Example:

str2 = "Silver Spoon"
print(str2.split(" "))      #Splits the string at the whitespace " ".

Output:

['Silver', 'Spoon']

There are various other string methods that we can use to modify our strings.

7. capitalize()

The capitalize() method turns only the first character of the string to uppercase and the rest other characters of the string are turned to lowercase. The string has no effect if the first character is already uppercase.

Example:

str1 = "hello"
capStr1 = str1.capitalize()
print(capStr1)
str2 = "hello WorlD"
capStr2 = str2.capitalize()
print(capStr2)

Output:

Hello
Hello world

8. center() :

The center() method aligns the string to the center as per the parameters given by the user.

Example:

str1 = "Welcome to the Console!!!"
print(str1.center(50))

Output:

            Welcome to the Console!!!

We can also provide padding character. It will fill the rest of the fill characters provided by the user.

Example:

str1 = "Welcome to the Console!!!"
print(str1.center(50, "."))

Output:

............Welcome to the Console!!!.............

9. count()

The count() method returns the number of times the given value has occurred within the given string.

Example:

str2 = "Abracadabra"
countStr = str2.count("a")
print(countStr)

Output:

4

10. endswith()

The endswith() method checks if the string ends with a given value. If yes then return True, else return False.

Example 1:

str1 = "Welcome to the Console !!!"
print(str1.endswith("!!!"))

Output:

True

Example 2:

str1 = "Welcome to the Console !!!"
print(str1.endswith("Console"))

Output:

False

We can even also check for a value in-between the string by providing start and end index positions.

Example:

str1 = "Welcome to the Console !!!"
print(str1.endswith("to", 4, 10))

Output:

True

11. find()

The find() method searches for the first occurrence of the given value and returns the index where it is present. If given value is absent from the string then return -1.

Example:

str1 = "He's name is Dan. He is an honest man."
print(str1.find("is"))

Output:

10

As we can see, this method is somewhat similar to the index() method. The major difference being that index() raises an exception if value is absent whereas find() does not.

Example:

str1 = "He's name is Dan. He is an honest man."
print(str1.find("Daniel"))

Output:

-1

12. index()

The index() method searches for the first occurrence of the given value and returns the index where it is present. If given value is absent from the string then raise an exception.

Example:

str1 = "He's name is Dan. Dan is an honest man."
print(str1.index("Dan"))

Output:

13

As we can see, this method is somewhat similar to the find() method. The major difference being that index() raises an exception if value is absent whereas find() does not.

Example:

str1 = "He's name is Dan. Dan is an honest man."
print(str1.index("Daniel"))

Output:

ValueError: substring not found

13. isalnum()

The isalnum() method returns True only if the entire string only consists of A-Z, a-z, 0-9. If any other characters or punctuations are present, then it returns False.

Example 1:

str1 = "WelcomeToTheConsole"
print(str1.isalnum())

Output:

True

Example 2:

str1 = "Welcome To The Console"
print(str1.isalnum())
str2 = "Hurray!!!"
print(str2.isalnum())

Output:

False
False

14. isalpha()

The isalnum() method returns True only if the entire string only consists of A-Z, a-z. If any other characters or punctuations or numbers(0-9) are present, then it returns False.

Example 1:

str1 = "Welcome"
print(str1.isalpha())

Output:

True

Example 2:

tr1 = "I'm 18 years old"
print(str1.isalpha())
str2 = "Hurray!!!"
print(str2.isalnum())

Output:

False
False

15. islower()

The islower() method returns True if all the characters in the string are lower case, else it returns False.

Example 1:

str1 = "hello world"
print(str1.islower())

Output:

True

Example 2:

str1 = "welcome Mike"
print(str1.islower())
str2 = "Hurray!!!"
print(str2.islower())

Output:

False
False

16. isprintable()

The isprintable() method returns True if all the values within the given string are printable, if not, then return False.

Example 1:

str1 = "We wish you a Merry Christmas"
print(str1.isprintable())

Output:

True

Example 2:

str2 = "Hello, \\t\\t.Mike"
print(str2.isprintable())

Output:

False

17. isspace()

The isspace() method returns True only and only if the string contains white spaces, else returns False.

Example 1:

str1 = "        "       #using Spacebar
print(str1.isspace())
str2 = "        "       #using Tab
print(str2.isspace())

Output:

True
True

Example 2:

str1 = "Hello World"
print(str1.isspace())

Output:

False

18. istitle()

The istitile() returns True only if the first letter of each word of the string is capitalized, else it returns False.

Example 1:

str1 = "World Health Organization"
print(str1.istitle())

Output:

True

Example 2:

str2 = "To kill a Mocking bird"
print(str2.istitle())

Output:

False

19. isupper()

The isupper() method returns True if all the characters in the string are upper case, else it returns False.

Example 1:

str1 = "WORLD HEALTH ORGANIZATION"
print(str1.isupper())

Output:

True

Example 2:

str2 = "To kill a Mocking bird"
print(str2.isupper())

Output:

False

20. replace()

The replace() method can be used to replace a part of the original string with another string.

Example:

str1 = "Python is a Compiled Language."
print(str1.replace("Compiled", "Interpreted"))

Output:

Python is a Interpreted Language.

21. startswith()

The endswith() method checks if the string starts with a given value. If yes then return True, else return False.

Example 1:

str1 = "Python is a Interpreted Language"
print(str1.startswith("Python"))

Output:

True

Example 2:

str1 = "Python is a Interpreted Language"
print(str1.startswith("a"))

Output:

False

We can even also check for a value in-between the string by providing start and end index positions.

Example:

str1 = "Python is a Interpreted Language"
print(str1.startswith("Inter", 12, 20))

Output:

True

22. swapcase()

The swapcase() method changes the character casing of the string. Upper case are converted to lower case and lower case to upper case.

Example:

str1 = "Python is a Interpreted Language"
print(str1.swapcase())

Output:

pYTHON IS A iNTERPRETED lANGUAGE

23. title()

The title() method capitalizes each letter of the word within the string.

Example:

str1 = "He's name is Dan. Dan is an honest man."
print(str1.title())

Output:

He'S Name Is Dan. Dan Is An Honest Man.

Format Strings in Python

What if we want to join two separated strings in python?

We can perform concatenation to join two or more separate strings.

Example:

str4 = "Captain"
str5 = "America"
str6 = str4 + " " + str5
print(str6)

Output:

Captain America

In the above example, we saw how one can concatenate two strings. But how can we concatenate a string and an integer?

name = "Guzman"
age = 18
print("My name is" + name + "and my age is" + age)

Output:

TypeError: can only concatenate str (not "int") to str

As we can see, we cannot concatenate a string to another data type.

So what’s the solution?

We make the use of format() method. The format() methods places the arguments within the string wherever the placeholders are specified.

Example:

name = "Guzman"
age = 18
statement = "My name is {} and my age is {}."
print(statement.format(name, age))

Output:

My name is Guzman and my age is 18.

We can also make the use of indexes to place the arguments in specified order.

Example:

quantity = 2
fruit = "Apples"
cost = 120.0
statement = "I want to buy {2} dozen {0} for {1}$"
print(statement.format(fruit,cost,quantity))

Output:

I want to buy 2 dozen Apples for $120.0

Escape Characters

Escape Characters are very important in python. It allows us to insert illegal characters into a string like a back slash, new line or a tab.

Single/Double Quote: used to insert single/double quotes in the string.

Example:

str1 = "He was \\"Flabergasted\\"."
str2 = 'He was \\'Flabergasted\\'.'
print(str1)
print(str2)

Output:

He was "Flabergasted".
He was 'Flabergasted'.

1. New Line: inserts a new line wherever specified.

Example:

str1 = "I love doing Yoga. \\nIt cleanses my mind and my body."
print(str1)

Output:

I love doing Yoga.
It cleanses my mind and my body.

2. Tab: inserts a tab wherever specified.

Example:

str2 = "Hello \\t\\tWorld \\t!!!"
print(str2)

Output:

Hello           World   !!!

3. Backspace: erases the character before it wherever it is specified.

Example:

str2 = "Hello  \\bWorld !!!"
print(str2)

Output:

Hello World !!!

4. Backslash: used to insert a backslash into a string in python.

Example:

str3 = "What will you eat? Apple\\\\Banana"
print(str3)

Output:

What will you eat? Apple\\Banana

Conclusion

Strings are an essential part of Python programming, and mastering string manipulation techniques is crucial for becoming proficient in Python development. By understanding the basic operations, string methods, formatting options, and advanced manipulation techniques covered in this guide, you’ll be well-equipped to handle a wide range of string-related tasks in your Python projects. Whether you’re a beginner or an experienced programmer, strings are a fundamental building block that you’ll use extensively throughout your Python journey.

Frequently Asked Questions