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Python Strings

In Python, a string is a sequence of characters. For example, “hello” is a string containing a sequence of characters ‘h’, ‘e’, ‘l’, ‘l’, and ‘o’.

We use single quotes or double quotes to represent a string in Python. For example,

				
					# create a string using double quotes
string1 = "Python programming"

# create a string using single quotes
string1 = 'Python programming'

Here, we have created a string variable named string1. The variable is initialized with the string “Python Programming”.

Example: Python String:-

				
					# create string type variables

name = "Python"
print(name)

message = "I love Python."
print(message)
Run Code

Output:-

				
					Python
I love Python.

In the above example, we have created string-type variables: name and message with values “Python” and “I love Python” respectively.

Here, we have used double quotes to represent strings, but we can use single quotes too.

Access String Characters in Python

We can access the characters in a string in three ways.

  • Indexing: One way is to treat strings as a list and use index values. For example,
				
					greet = 'hello'

# access 1st index element
print(greet[1]) # "e"
Run Code
  • Negative Indexing: Similar to a list, Python allows negative indexing for its strings. For example,
				
					greet = 'hello'

# access 4th last element
print(greet[-4]) # "e"
Run Code
  • Slicing: Access a range of characters in a string by using the slicing operator colon :. For example,
				
					greet = 'Hello'

# access character from 1st index to 3rd index
print(greet[1:4])  # "ell"
Run Code

Note: If we try to access an index out of the range or use numbers other than an integer, we will get errors.

Python Strings are Immutable

In Python, strings are immutable. That means the characters of a string cannot be changed. For example,

				
					message = 'Hola Amigos'
message[0] = 'H'
print(message)
Run Code

Output:-

				
					TypeError: 'str' object does not support item assignment

However, we can assign the variable name to a new string. For example,

				
					message = 'Hola Amigos'

# assign new string to message variable
message = 'Hello Friends'

print(message); # prints "Hello Friends"
Run Code

Python Multiline String

We can also create a multiline string in Python. For this, we use triple double quotes “”” or triple single quotes ”’. For example,

				
					# multiline string 
message = """

				
			
				
					Never gonna give you up
Never gonna let you down
"""

print(message)
Run Code

Output:-

				
					Never gonna give you up
Never gonna let you down

In the above example, anything inside the enclosing triple quotes is one multiline string.

Python String Operations

Many operations can be performed with strings, which makes it one of the most used data types in Python.

1. Compare Two Strings

We use the == operator to compare two strings. If two strings are equal, the operator returns True. Otherwise, it returns False. For example,

				
					str1 = "Hello, world!"
str2 = "I love Swift."
str3 = "Hello, world!"

# compare str1 and str2
print(str1 == str2)

# compare str1 and str3
print(str1 == str3)
Run Code

Output:-

				
					False
True

In the above example,

  1. str1and str2 are not equal. Hence, the result is False.
  2. str1and str3 are equal. Hence, the result is True.

2. Join Two or More Strings

In Python, we can join (concatenate) two or more strings using the + operator.

				
					greet = "Hello, "
name = "Jack"

# using + operator
result = greet + name
print(result)

# Output: Hello, Jack
Run Code

In the above example, we have used the + operator to join two strings: greet and name.

Iterate Through a Python String

We can iterate through a string using a for loop. For example,

				
					greet = 'Hello'

# iterating through greet string
for letter in greet:
    print(letter)
Run Code

Output:-

				
					H
e
l
l
o

Python String Length

In Python, we use the len() method to find the length of a string. For example,

				
					greet = 'Hello'

# count length of greet string
print(len(greet))

# Output: 5
Run Code

String Membership Test

We can test if a substring exists within a string or not, using the keyword in.

				
					print('a' in 'program') # True
print('at' not in 'battle') # False

Methods of Python String

Besides those mentioned above, there are various string methods present in Python. Here are some of those methods:

upper()

Converts the string to uppercase

lower()

Converts the string to lowercase

partition()

Returns a tuple

replace()

Replaces substring inside

find()

Returns the index of the first occurrence of substring

rstrip()

Removes trailing characters

split()

Splits string from left

startswith()

Checks if string starts with the specified string

isnumeric()

Checks numeric characters

index()

Returns index of substring

Escape Sequences in Python

The escape sequence is used to escape some of the characters present inside a string.

Suppose we need to include both a double quote and a single quote inside a string,

				
					example = "He said, "What's there?""

print(example) # throws error
Run Code

Since strings are represented by single or double quotes, the compiler will treat “He said, ” as a string. Hence, the above code will cause an error.

To solve this issue, we use the escape character \ in Python.

				
					# escape double quotes
example = "He said, \"What's there?\""

# escape single quotes
example = 'He said, "What\'s there?"'

print(example)

# Output: He said, "What's there?"
Run Code

Here is a list of all the escape sequences supported by Python.

Escape Sequence

Description

\\

Backslash

\’

Single quote

\”

Double quote

\a

ASCII Bell

\b

ASCII Backspace

\f

ASCII Formfeed

\n

ASCII Linefeed

\r

ASCII Carriage Return

\t

ASCII Horizontal Tab

\v

ASCII Vertical Tab

\ooo

Character with octal value ooo

\xHH

Character with hexadecimal value HH

Python String Formatting (f-Strings)

Python f-Strings makes it easy to print values and variables. For example,

				
					name = 'Cathy'
country = 'UK'

print(f'{name} is from {country}')
Run Code

Output:-

				
					Cathy is from UK

Here, f'{name} is from {country}’ is an f-string.

This new formatting syntax is powerful and easy to use. From now on, we will use f-Strings to print strings and variables.

Boolean= Python bool()

The bool() method takes a specified argument and returns its boolean value.

Example-

				
					test = 1

# returns boolean value of 1
print(test, 'is', bool(test))


# Output: 1 is True

bool() Syntax

The syntax of bool() is:

				
					bool(argument)

bool() Parameter

The bool() method takes in a single parameter:

  • argument – whose boolean value is returned

bool() Return Value

The bool() method returns:

           False – if argument is empty, False, 0 or None

           True – if argument is any number (besides 0), True or a string

Example 1: Python bool() with True Arguments

				
					test = 254
# bool() with an integer number
print(test, 'is', bool(test))


test1 = 25.14
# bool() with a floating point number
print(test1, 'is', bool(test1))


test2 = 'Python is the best'
# bool() with a string
print(test2, 'is', bool(test2))


test3 = True
# bool() with True
print(test3, 'is', bool(test3))

Output:-

				
					254 is True
25.14 is True
Python is the best is True
True is True

In the above example, we have used the bool() method with various arguments like integer, floating point numbers, and string.

Here, the method returns True values for arguments like 25, 25.14, ‘Python is a String’, and True

Example 2: bool() with False Arguments

				
					test = []
# bool() with an empty argument
print(test, 'is' ,bool(test))


test1 = 0
# bool() with zero
print(test1, 'is' ,bool(test1))


test2 = None
# bool() with none
print(test2, 'is' ,bool(test2))


test3 = False
# bool() with False
print(test3, 'is' ,bool(test3))

Output:-

				
					[] is False
0 is False
None is False
False is False

In the above example, the bool() method returns False values for arguments like 0, None, False and [].