Linux Advise
- Aug 15, 2020
- 5 min read

Python Strings

We have covered the number data type in the last article and now we are going to study about strings. Strings are a sequence of characters enclosed between either single quotes or double-quotes. eg. 'Hello' "Linux Advise"

Strings

String literals in python are surrounded by either single quotation marks or double quotation marks.

'hello' is the same as "hello".

You can display a string literal with the print() function:

Example:


print("Hello")
print('Hello')

Output:


Hello
Hello

Because strings are ordered sequences, we can use slicing and indexing to grab sub-section of the string.

Indexing notation uses [] notation after the string.

Indexing allows you to grab a single character from a string

Assign String to a Variable

Assigning a string to a variable is done with the variable name followed by an equal sign and the string:

Example:


a ="Hello"
print(a)

Output:


Hello

Multi-line Strings

You can assign a multi-line string to a variable by using three quotes:

Example:

You can use three double quotes:


a ="""Welcome to Linux advise
this article is for python string operations
and functions """
print(a)

Output:


Welcome to Linux advise
this article is for python string operations
and functions

Example:

Or three single quotes:


a ='''Welcome to Linux advise
this article is for python string operations
and functions'''
print(a)

Output:


 Welcome to Linux advise
 this article is for python string operations 
 and functions

How to access characters in a string?

We can access individual characters using indexing and a range of characters using slicing. The index starts from 0.
Trying to access a character out of index range will raise an IndexError. The index must be an integer.
We can't use floats or other types, this will result into TypeError.
Python allows negative indexing for its sequences.
The index of -1 refers to the last item, -2 to the second last item, and so on. We can access a range of items in a string by using the slicing operator :(colon).

Example:


# Accessing string characters in Python
str = 'Linux Advise'
print('str = ', str)

Output:


str =  Linux Advise

Example:


# First character
print('str[0] = ', str[0])

Output:


str[0] =  L

Example:


# Last character
print('str[-1] = ', str[-1])

Output:


str[-1] =  e

Example:


# Slicing 2nd to 5th character
print('str[1:5] = ', str[1:5])

Output:


str[1:5] =  inux

Example:


# Slicing 6th to 2nd last character
print('str[5:-2] = ', str[5:-2])

Output:


str[5:-2] =   Advi

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

Example:


# Index must be in range
my_string = 'Linux Advise'
my_string[15]

Output:


Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
IndexError: string index out of range

Example:


# Index must be an integer
my_string = 'Linux Advise'
my_string[1.5]

Output:


Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: string indices must be integers

Python String Operations

There are many operations that can be performed with a string which makes it one of the most used data types in Python.

We can do a number of operations on strings.

If in case the string consists of a single quote, then string should be placed between double quotes

Example:


print("I don't lie")

Output:


I don't lie

We can have newlines and Tab-separated strings as well as shown below

Example:


print("Welcome \n to \n Linux \n Advise ")
Output:
Welcome 
to 
Linux 
Advise 

print("Welcome \t to \t Linux \t Advise ")
Output:
Wecome 	 to 	 linux 	 Advise

Concatenation of Two or More Strings

Joining of two or more strings into a single one is called concatenation.

The + operator does this in Python. Simply writing two string literals together also concatenates them.

The * operator can be used to repeat the string for a given number of times.

Example:


# Python String Operations
str1 = 'Linux'
str2 ='Advise'
# using +
print('str1 + str2 = ', str1 + str2)

Output:


str1 + str2 =  LinuxAdvise

Example:


# Using *
print('str1 * 3 =', str1 * 3)

Output:


str1 * 3 = LinuxLinuxLinux

To calculate the length of the string we can use len() function

Example:


len("linuxadvise")

Output:

The format() Method for Formatting Strings

The format() method that is available with the string object is very versatile and powerful in formatting strings. Format strings contain curly braces {} as placeholders or replacement fields that get replaced.

We can use positional arguments or keyword arguments to specify the order.

Example:


# Python string format() method
# Default(implicit) order
default_order = "{}, {} and {}".format('John','Bill','Sean')
print(&#x