Section (1) – Introduction to Strings in Python
In Python, a string is a sequence of characters enclosed within single quotes (‘ ‘) or double quotes (” “). It is one of the built-in data types in Python and is widely used in various applications.
Creating a String
We can create a string by assigning a value enclosed within quotes to a variable. For example:
string_variable = "This is a string."
We can also use single quotes to create a string, as shown below:
string_variable = 'This is also a string.'
Accessing Characters in a String
We can access individual characters in a string using indexing. In Python, indexing starts at 0, so the first character in a string has an index of 0, the second character has an index of 1, and so on. For example:
string_variable = "Hello, World!" print(string_variable) # Output: H print(string_variable) # Output: e
We can also use negative indexing to access characters from the end of the string. For example:
string_variable = "Hello, World!" print(string_variable[-1]) # Output: ! print(string_variable[-2]) # Output: d
We can extract a portion of a string using string slicing. String slicing allows us to create a new string from a portion of an existing string. The syntax for string slicing is
string_variable[start_index:end_index]. For example:
string_variable = "Hello, World!" print(string_variable[0:5]) # Output: Hello
If we omit the
start_index, Python assumes it to be 0. If we omit the
end_index, Python assumes it to be the end of the string. For example:
string_variable = "Hello, World!" print(string_variable[:5]) # Output: Hello print(string_variable[7:]) # Output: World!
We can concatenate two or more strings using the
+ operator. For example:
string1 = "Hello" string2 = "World" string3 = string1 + " " + string2 print(string3) # Output: Hello World
We can also repeat a string multiple times using the
* operator. For example:
string_variable = "Hello" print(string_variable * 3) # Output: HelloHelloHello
Python provides several built-in string methods that we can use to manipulate strings. Some of the commonly used string methods are:
len(string): Returns the length of the string.
string.lower(): Converts all the characters in the string to lowercase.
string.upper(): Converts all the characters in the string to uppercase.
string.replace(old, new): Replaces all occurrences of the
oldsubstring with the
string.split(separator): Splits the string into a list of substrings based on the
string.strip(): Removes any leading or trailing whitespace characters from the string.
String formatting is the process of inserting values into a string. Python provides several ways to perform string formatting, including using the
% operator, the
format() method, and f-strings.
% operator is a common way to format strings in Python. It allows you to specify placeholders in a string that will be replaced with values at runtime. The syntax for using the
% operator is as follows:
string % values