Variables that hold text are of string data type. Strings are sequences of characters. For example, “coder” is a string containing sequence of characters ‘c’, ‘o’, ‘d’,‘ e’ and ‘r’.

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

my_string = "I am the she coder"
string_1 = 'Hello'

Creating Multiline Strings

To create multiline strings in Python, we use triple double quotes """ or triple single quotes '''.

multi_string = """
Strings are sequences of characters
We use single quotes or double quotes to represent a string in Python
"""

ms_string = '''
Strings are sequences of characters
We use single quotes or double quotes to represent a string in Python
'''

print(multi_string)
print(ms_string)

Getting The Length Of A String

We use the len() method to know the total number of characters in a string. Remember, even the blank spaces are counted as characters in a string.

my_string = "I am the she coder"

print(len(my_string)) #18

Accessing String Characters

There are three ways to access characters in a string

1. Indexing: In Python indexing of strings starts from 0 till n-1, where n is the size of string. So characters in string of size n, can be accessed from 0 to n-1.

string2 = "hello"
#accessing 1st character in string2
print(string2[0]) # "h"

#accessing 2nd character in string2
print(string2[1]) # "e"

#accessing 4th character in string2
print(string2[4]) # "o"

2. Negative Indexing: We can access characters from the back of a String using negative indexing.

string2 = "hello"
#accessing last character in string2
print(string2[-1]) # "o"

#accessing 2nd last character in string2
print(string2[-2]) # "l"

#accessing 4th last character in string2
print(string2[-4]) # "e"

Note:- Accessing an index out of the range will cause an IndexError. Also, only integers are allowed to be passed as an index, float or other types will cause a TypeError.

string2 = "hello"
print(string2[5]) # IndexError: string index out of range

print(string2[1.5]) # TypeError: string indices must be integers

3. Slicing: Access a range of characters in a string by using the slicing operator colon :

string2 = "hello"

#accessing from 0 character to 2nd character
print(string2[0:3]) # 'hel'

#accessing from 3rd character to last character
print(string2[3:]) # 'lo'

Strings Are Immutable

The characters of a string cannot be changed. 

string2 = "hello"
string2[0] = 'j'
print(string2) # TypeError: 'str' object does not support item assignment

Reversing A String

We can Reverse a string by writing [::-1] and the string will be reversed.

string2 = "hello"

print(string2[::-1]) # "olleh" 

Joining two strings

We can join (concatenate) two or more strings using the + operator.

string_1 = "My name is "
string_2 = "Anam"
print(string_1 + string_2) # My name is Anam
print("Hey " + string_2) # Hey Anam

Iterating Through a Python String

We can iterate or go through the characters of a string one by one using a for loop.

string2 = "hello"

for character in string2:
    print(character)

Check If A Substring Exists In A String

We can determine whether or not a given element is a component of a specific string using (in) & (not in)

string2 = "hello"

print('e' in 'hello') # True
print('ll' not in 'hello') # False

Escape Sequence

If we want to print a text like She said "Hello". We cannot write it by using a single quote or double quote. It will show a syntax error. To avoid error we use escape sequence.

string_1 = "She said \"Hello\" "
print(string_1)

String Formatting (f-Strings)

You can use the format() method of str to insert values into the replacement field {} with positional or keyword arguments

name = 'Grace'
nationality = 'Turkish'

print(f'Her name is {name} and she is {nationality}') 

The Str() Constructor

Python has a built-in function str(), which returns a string representation of any object.

x = str(7) 
y = str(6.5) 
z = str(True) 
print(type(x)) # <class 'str'>
print(type(y)) # <class 'str'>
print(type(z)) # <class 'str'>

String Methods

Python has a set of built-in methods that you can use on string objects. Here are few of them:

Upper() – The upper() method returns the string in upper case.

Lower() – The lower() method returns the string in lower case.

Capitalize() – The capitalize() method converts the first character of the string in uppercase and rest of the other characters into lowercase.

Replace() – The replace() method replaces a specified phrase with another specified phrase.

s = "I like Coding!" 

print(s.upper()) # I LIKE CODING!

print(s.lower()) # i like coding!

print(s.capitalize()) # I like coding!

print(s.replace("Coding","Writing") # I like Writing!

Here are list of some more string methods :