Python Strings

A String means a sequence of characters. Python strings are always surrounded by single quote(') or double qoute (") even triple quote(''') characters. such as 'hello' or "hello" or '''hello'''. By the quotation mark Python knows where the string begins and ends.

Example:

my_string1 = "Hello World!"
my_string2 = 'Hello World!'
my_string3 = '''Hello World!'''
my_string4 = """Hello World!"""
print(my_string1)
print(my_string2)
print(my_string3)
print(my_string4)

Output:

Hello World!
Hello World!
Hello World!
Hello World!

Indexing and Slicing of a String

You can access the character of a string using the bracket. The expression in brackets is called an index. In python the index always starts with 0. If you specify an index you will get the character at that position in the string.

Example:

country = "Bangladesh"
letter = country[1]
print(letter)

Output:

a

The example extracts the character at index position 1 from the country variable and assigns it to the letter variable. As the index starts with 0 the output of the example is a.

You can also specify a range from one index to another.

Example:

country = "Bangladesh"
letter = country[2:5]
print(letter)

Output:

ngl

Negative indexing can also be used. It starts from the last value. To get the characters from 5 to 1 position you should start the count from the end of the string.

Example:

country = "Bangladesh"
letter = country[-5:-2]
print(letter)

Output:

ade

Length of a String

To get length of a string there is a built-in function in Python. len() is the built-in function that returns the number of character in a string.

Example:

country = "Bangladesh"
length = len(country)
print(length)

Output:

10

Useful String Methods

Python has a set of built-in methods. Here some useful methods are described:

upper(): This method returns a new string where all the letter in the original string have been converted to uppercase.

Example:

country = "Bangladesh"
country = country.upper()
print(country)

Output:

BANGLADESH

lower(): This method returns a new string where all the letter in the original string have been converted to lowercase.

Example:

country = "Bangladesh"
country = country.lower()
print(country)

Output:

bangladesh

strip(): This method removes whitespace from the beginning or the end.

Example:

country = " Bangladesh "
country = country.strip()
print(country)

Output:

Bangladesh

replace(): This method removes whitespace from the beginning or the end.

Example:

mystring = "Rahim"
mystring = mystring.replace("R","F")
print(mystring)

Output:

Fahim

split(): This method removes whitespace from the beginning or the end.

Example:

mystring = "I love my country"
mystring = mystring.split(",")
print(mystring)

Output:

['I', ' love', ' my', ' country']

String Methods

There are a set of built-in methods in python which you can use on strings.