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Python String – A Comprehensive Tutorial with Examples

Q: How can I check if a string starts and ends with a specific substring?

The startswith() method checks whether a string starts with a particular substring.

Q: How do I convert a string to a list of characters or vice versa?

The list() method converts a string to a list of characters, and we can use the ‘join()’ method to concatenate a list of characters into a single string.

Q: How do I find the index of a substring within a string?

We can use the ‘find()’ method to find the index of the first occurrence of a substring within a string. If the substring is not found, It will return ‘-1’.

Basics of Python

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In Python, String is used for storing the URL(Uniform Resource Locator), file paths, JSON data, and virtually any textual information. Python strings are sequences of individual characters, which means we can access the specific characters of a string using indexing and slicing.

Syntax of Python String

str=” My Name is Python”

print(str)

What is a String in Python?

In the Python programming language, a string is a sequence of characters within either single quotes, double quotes, or triplet quotes. Strings can contain letters, numbers, symbols, and whitespace characters. Python strings are immutable, which means the content of the string cannot be changed once it is defined.

Creating a Python String

In the Python programming language, we make the strings by enclosing them in single or double quotation marks. Python programming language also supports the triple quotes for defining the Python programming language.

Python String Example

str='Hello Python Programming language'

print(str)

str2 = "Hello Python 2"

print(str2)

str3 = “”" Hello Python 3"””

print(str3)

Python String Indexes

In the Python programming language, we also can access individual characters from the string using the indexes. Each character in a string has a unique index. It starts from 0 for the first character, 1 for the second character, and so on. In the Python programming language, we can also access the string using the negative indexes. We can access the end of the string, with -1 representing the last character, -2 representing the second to last character, and so far.

Python Program

str="Programming"

print("Positive Indexing")

print(str[0])

print(str[1])

print(str[2])


# negative indexing


print("Negative Indexing")

print(str[-1])

print(str[-2])

print(str[-3])

Output

Positive Indexing

P

r

o

Negative Indexing

g

n

I

Accessing Characters in Python String

In Python, we can access the string using indexing. Indexing allows negative and positive characters from the back of the string. For example, -1 refers to the last character of the string, -2 refers to the second-last character in the string, and so on.

Accessing the index out of the range will cause an IndexError in Python language.

Program

str = "herovired"

print(str[0])

Output

Strings Indexing and Splitting

String Indexing: In Python, a string is a sequence of characters. Using Python’s indexing, we can get the individual character by the single character. The index starts from 0, the second index is 1, and so on.

The following program demonstrates the example

Program

str = "Hello"

print(str[0])

print(str[1])

print(str[2])

print(str[3])

print(str[4])

Output

H

e

l

l

o

Splitting: We can split the string using the split() function in Python. This method splits a string into a list using a specified delimiter. The following program demonstrates the string splits().

Program

string = "one, two, three"

words = string.split(',')

print(words)

Output

['one', 'two', 'three']

Reversing a Python String

In the Python programming language, we also reverse a string using the string slice method. In this example, we will reverse a string by accessing the index. In slicing, we will not specify the first two parts of the slice. That indicates that we are considering the whole string, from the last point to the last index.

The following program demonstrates the reverse of a string.

Program

#Program to reverse a string

str2 = "helloworld"

print(str2[::-1])

Output

dlrowolleh

Deleting Strings in Python

String are immutable characters. In the simple world. After assigning the string, we cannot make any changes to it. We cannot make any changes to it. We cannot remove or delete any character of the string. But in Python, we can delete the whole string using the del keyword.

The following program demonstrates the model keyword in Python

Program

str = "Helloworld"

print(str)

del str ;

print(str)

Output

Helloworld

<class 'str'>

Updating/Reassigning Strings in Python

Strings are immutable. It means, we cannot change the string after the declaration. But we can reassess the string in Python. Stings cannot be completed with a new string. Let’s see the following example of string reassigning.

Program

message="Welcome to the Programming world"

print(message)

message="Hacking World" #reassigning a new string

print(message)

Output

Welcome to the Programming world

Hacking World

Python Escape Sequence

A character with a backslash () just before it is called an escape sequence or escape character. We use escape characters to perform specific tasks while running your program. Escape Sequence is used when a programmer wants to add double quotes or single quotes in a program. There are many escape sequence characters available in the Python language.

List of Escape Sequences Available in Python

Escape Sequence	Meaning
’	Single Quote
”	Double Quote
	Backslash
n	Newline
r	Carriage Return
t	Horizontal Tab
b	Backspace
f	Formfeed
v	Vertical Tab
0	Null Character
N{Name}	Unicode character named in database lookup
uxxxxxxxx	Unicode character with a 16-bit hex value
Uxxxxxxxx	A Unicode character with a 32-bit hex value
000	A character with octal value ooo
xhh	The character with a hex value

Python String Formatting

In Python, we can format the string data type with the use format() method, which is a versatile function for formatting strings in Python. The format method contains curly braces {} as a placeholder, which can hold the arguments according to the position or keyword to specify the order.

Example: In this example, we will declare a string containing curly brackets and pass the dynamic string in these curly braces.

Program

# Python Program for

# Formatting of Strings

# Default order

String1 = "{} {} {}".format('Hello', 'Programming', 'World')

print("Print String in default order: ")

print(String1)


# Positional Formatting

String1 = "{1} {0} {2}".format('Hello ', 'Programming', 'World')

print("nPrint String in Positional order: ")

print(String1)


# Keyword Formatting

String1 = "{l} {f} {g}".format(g='Hello', f='Computer', l='Programming')

print("nPrint String in order of Keywords: ")

print(String1)

Output

Print String in default order:

Hello Programming World

Print String in Positional order:

Programming Hello  World

Print String in order of Keywords:

Programming Computer Hello

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Iterate a String using a loop

We can also iterate the string using the while loop and for loop in Python language. Python allows access to the single characters in the string one by one using any loop.

Using a for-loop: The following program demonstrates the for-loop example in Python

str = "hello world"

for c in str:

print(c)

Output

h

e

l

l

o

w

o

r

l

d

Using a while loop: The following program iterates a String using a while loop.

string = "Hello World"

index = 0

while index < len(string):

print(string[index])

index += 1

Output

H

e

l

l

o

W

o

r

l

d

Useful Python String Operations

Python language provides various operations to manipulate strings efficiently. Here I am discussing the common operations that are performed in strings.

Logical Operators on String
String Template Class
Split a string
String Slicing
Find all duplicate characters in string
String formatting using %

Python String Constants

Built-in Function	Description
string.ascii_letter	Concatenation of the ascii_lowercaes and ascii_uppercae constants
string.ascii_lowercase	Concatenations of lowercase letters
string.ascii_uppercase	Concatenations of uppercase letters
string.digits	Digit in strings
string.letters	Concatenation of strings lowercase and uppercase
string.lowercase	A string must contain lowercase letters
string.octdigits	Octadigit in a string
string.punctuation	ASCII characters have punctuation characters.
string.printable	Strings of characters which are printable
Strig.endswith()	Return true if the string ends with a given suffix otherwise, this method returns false.
Strings.startswith()	This method returns true if a string starts with the given prefix otherwise. This method returns false.
String.isdigit()	This method returns true if all characters are digits otherwise. This method returns false.
String.isdecimal()	This method returns true if all characters are decimal
str.format()	This method allows substitution in an existing string
String.index	This method returns the position of the first occurrence of a substring in a string
replace()	This method returns the string where all strings are replaced with another string.
string.swapcase()	This method converts all uppercase characters to lowercase and vice versa of the given string.

Compare Strings in Python

We can compare the string in Python using the comparison operators (==,!=,<,> <=, >=) compare strings.

The following program demonstrates the comparison of the strings.

Program

string1  =  "apple"

string2  =  "Apple"


print(string1  ==  string2)

print(string1  !=  string2)

print(string1  <  string2)

print(string1  >  string2)

print(string1  <=  string2)

print(string1  >=  string2)

Output

False

True

False

True

False

True

String Membership Test

The string member is nothing much. It is the test to check if a substring is present in a certain string.

To check if a substring is present in a string, we can use the “in” operator. The result of this statement would be a boolean value. It will return true if the substring is present in the string; otherwise, it will return false.

Program

print('str' in 'str is present or not str')

print('word' in 'Harry Potter')

Output

True

False

Unicode String

In Python language, normal strings are stored internally as 8-bit ASCII, while Unicode strings are stored in 16-bit Unicode. Unicode strings allow you to work with different language and character sets.

The following program demonstrates the Unicode String example.

Program

# Creating a Unicode string directly

unicode_str = "Hello, 世界!"

print(unicode_str)

Output

Hello, 世界!

Multi-line Strings

We can also implement multi-line strings in the Python language. To do so, we use backlash, brackets, and triple quotes.

The following program demonstrates a multi string example in Python

Program

multiline_string = '''This is a

multiline

string.'''

print(multiline_string)


colors = ("multi-line string"

"red n"

"blue n"

"green n"

"yellow n"

)


print(colors)


x = "multiline String" 

"I love Python" 

"Python Language"

print(x)

Output

This is a

multiline

string.

multi-line string red

blue

green

yellow

Python String Methods

Python programming language offers a rich set of string methods that allow developers to manipulate and process text efficiently. These methods are essential for Python programmers. A string is a fundamental data type in the Python language. It is used in a wide range of applications. Below are some useful string methods, along with practical examples to demonstrate their usage.

upper(): This string method is used to convert a string into Uppercase
lower(): This string method is used to convert a string into lowercase
split(): This method divides a string into a list of substrings based on a delimiter
join(): This method joins the elements of an iterable into a single string, using the string as a delimiter.
find(): This method finds the first occurrence of the specified string otherwise, it will return the -1 if the value is not found.
count(): This method returns the number of characters that occur in the string
replace(): This method replaces a specified string with another specified string.

Program

text = "Hello, World!"

print(text.upper())  # Output: HELLO, WORLD!

print(text.lower())  # Output: hello, world!


text = "   Hello, World!   "

print(text.strip())  # Output: Hello, World!


text = "   Hello, World!   "

print(text.strip())  # Output: Hello, World!


text = "Python is versatile and powerful"

words = text.split()

print(words)  # Output: ['Python', 'is', 'versatile', 'and', 'powerful']


new_text = '-'.join(words)

print(new_text)  # Output: Python-is-versatile-and-powerful


text = "Python is powerful, and Python is easy to learn."

print(text.find("Python"))  # Output: 0

print(text.count("Python"))  # Output: 2


text = "Python is easy to learn"

new_text = text.replace("easy", "fun")

print(new_text)  # Output: Python is fun to learn

Output

HELLO, WORLD!

hello, world!

Hello, World!

Hello, World!

['Python', 'is', 'versatile', 'and', 'powerful']

Python-is-versatile-and-powerful

0

2

Python is fun to learn

List of String Methods in Python

Python has a rich set of string methods. Here is the list of in-built Python string methods.

Methods	Descriptions
center()	This method aligns the string in the center
count()	This method counts the string characters
encode()	This method encodes the string, using the specified encoding.
endsWith()	This method returns true if the string ends with a specified value; otherwise returns false.
expandtabs()	This method sets the tab size to the specified number
find()	This method finds the first occurrence of the string if the string is not found, it will return -1
strip()	This method removes any leading and trailing whitespaces.
format_map()	This method returns a dictionary value.
index()	This method finds the first occurrence of species value
isalnum()	This method returns true if the string is alphanumeric otherwise, It will return false.
isalpha()	This method returns true if all the characters are alphabet
isdecimal()	This method returns true if all the characters are decimal; otherwise, it will return false
isdigit()	This method returns true if all the characters are digits otherwise, it will return false.
isidentifier()	This method returns true if the string is a valid identifier otherwise, it returns false.
islower()	This method returns true if all the characters are lower otherwise, it will return false.
isnumeric()	This method returns true if all the characters are numeric otherwise, It will return false.
isprintable()	This method returns true if all the characters are printable otherwise, it will return false.
lower()	This method returns a string where all the characters are lower
lstrip()	This method removes any leading characters from the strip
maketrans()	This method returns a mapping table
partition()	This method searches the specified string in the string.
replace()	This method replaces a specified string with a specified string.

isprintable()	This method returns true if all the characters in the string are printable. If not, it returns false.
istitle()	This method returns true if all words are strings are titles otherwise returns false
rfind()	This method returns the highest index of the substring
splitlines()	This method splits the lines at line boundaries
zfill()	This method adds zeros(0) at the beginning of the string until it reaches the specified length of the string.
rpartition()	This method splits the string into three parts

Conclusion

In this article, we learned about various types of string methods in the Python programming language. We learned about the reverse() method for reversing the string and the replace() method for replacing the specified string with a specific string. Python provides a rich set of built-in methods for string manipulations, allowing you to perform various operations efficiently. If you want to learn more about the Python programming language, you can check out the Accelerator Program in Business Analytics and Data Science.

FAQs

What are Python string methods?

Python string methods are built-in methods in Python that operate on strings. These allow you to perform various kinds of operations on strings, like manipulation, searching, formatting, replacement, etc.

How do I convert the string into uppercase in Python?

In the Python programming language, we can use the upper() case method, which converts a string into uppercase.

How can I check if a string starts and ends with a specific substring?

The startswith() method checks whether a string starts with a particular substring.

How do I convert a string to a list of characters or vice versa?

The list() method converts a string to a list of characters, and we can use the ‘join()’ method to concatenate a list of characters into a single string.

How do I find the index of a substring within a string?

We can use the ‘find()’ method to find the index of the first occurrence of a substring within a string. If the substring is not found, It will return ‘-1’.

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