Python Strings

String is a commonly used data type in Python. It is simply a series of characters. To define a string literal in Python, you just place your characters within single quotes or double quotes.

var1 = "This is a String in Python"
var2 = 'You can also use single quotes'

You can access any character in a string with its index value. Python uses 0-based indexing, so first character in a string has index 0, second character has index 1. You can also use negative indexes to access characters at the end. For instance, to access the last character in a string, you can use index -1.

var1 = "Hello World!"

print(var1[0])         # prints H (first character)
print(var1[-1])        # prints ! (last character)

Slicing a String

To slice a string, you can use Python’s slicing operator [].

Slicing Operator
var[start:stop:step]

start: Specifies the start of the index value (Inclusive). If not given, the default value is 0.
stop: Specifies the end of the index value (Exclusive). If not given, the default value is the last element.
step: Specifies the number of steps to jump between start and stop index. If not given, the default value is 1.

var1 = "Hello World!"

print(var1[0:2])            # First two characters ("He")
print(var1[:2])             # If start index is not specified,
                            # default value is 0

print(var1[6:8])            # Two characters from 7th character
                            # (index 7th charater is 6 )
                            # ("Wo")

print(var1[-2:])            # Last two characters
                            # ("d!")

print(var1[::-1])          # Reverse the string (step = -1)
                           # ("!dlroW olleH")

Multiline Strings

To create a multiline string in Python, you can enclose the string in triple double quotes (""") or triple single quotes (''').

print("""Triple double quotes are used
in this example to create multi-line string.
You can also use triple single quotes.""")

String Formatting

You can format a string using format() method. Placeholder for your data is identified with curly braces {}.

print("My name is {}!".format("Michael"))
# My name is Michael!

To access values in a formatted string, you can use index numbers (index of first value is 0, second value is 1, and so on).

print("Hello {1}. My name is {0}!".format("George", "Michael"))
# Hello Michael. My name is George!

The in Operator

In operator is used to check if a string contains a substring. It returns true if a substring exists in the main string. Otherwise, it returns false.

main_colors = "red orange yellow green blue indigo violet"

print("red" in main_colors)      # True
print("brown" in main_colors)    # False

Escape Characters

There are some special characters that you cannot use directly in a string. To use these special characters, you need to prepend them with a backslash (\).

For example, to put a double quote in a string, you need to prepend it with backslash \".

print("Learning \"Python\" is fun")
# Learning "Python" is fun

Commonly used escape characters are:

Built-in String Methods

There are many useful built-in string methods in Python. Commonly used string methods are described below.

The upper() and lower() methods are used to convert all letters in a string to uppercase or lowercase.

print("Hello World!".upper())      # HELLO WORLD!
print("Hello World!".lower())      # hello world!

The startswith() and endswith() methods are used to check whether a string starts with or ends with a string. These methods return true if the string starts with (or ends with) the string specified in the parameter.

print("Hello World!".startswith("Hello"))    # True
print("Hello World!".endswith("World!"))     # True

The strip(), rstrip(), and lstrip() methods are used to trim strings (i.e. remove whitespace characters). lstrip() method is used to remove any whitespace character at the beginning of a string, rstrip() method is used to remove whitespace characters at the end of a string, strip() method is used to remove whitespace characters at both sides.

print("   Hello World!   ".lstrip())         # "Hello World!   "
print("   Hello World!   ".rstrip())         # "   HelloWorld!"
print("   Hello World!   ".strip())          # "HelloWorld!"