In Python, a string is a sequence of characters. For example, "hello" is a string containing a sequence of characters 'h', 'e', 'l', 'l', and 'o'.
We use single quotes or double quotes to represent a string in Python. For example,
# create a string using double quotes
string1 = "Python programming"
# create a string using single quotes
string1 = 'Python programming'
Here, we have created a string variable named string1. The variable is initialized with the string "Python Programming".
Example: Python String
# create string type variables
name = "Python"
print(name)
message = "I love Python."
print(message)
Output
Python I love Python.
In the above example, we have created string-type variables: name and message with values "Python" and "I love Python" respectively.
Here, we have used double quotes to represent strings, but we can use single quotes too.
Access String Characters in Python
We can access the characters in a string in three ways.
- Indexing: One way is to treat strings as a list and use index values. For example,
greet = 'hello'
# access 1st index element
print(greet[1]) # "e"
- Negative Indexing: Similar to a list, Python allows negative indexing for its strings. For example,
greet = 'hello'
# access 4th last element
print(greet[-4]) # "e"
- Slicing: Access a range of characters in a string by using the slicing operator colon
:. For example,
greet = 'Hello'
# access character from 1st index to 3rd index
print(greet[1:4]) # "ell"
Note: If we try to access an index out of the range or use numbers other than an integer, we will get errors.
Python Strings are Immutable
In Python, strings are immutable. That means the characters of a string cannot be changed. For example,
message = 'Hola Amigos'
message[0] = 'H'
print(message)
Output
TypeError: 'str' object does not support item assignment
However, we can assign the variable name to a new string. For example,
message = 'Hola Amigos'
# assign new string to message variable
message = 'Hello Friends'
print(message); # prints "Hello Friends"
Python Multiline String
We can also create a multiline string in Python. For this, we use triple double quotes """ or triple single quotes '''. For example,
# multiline string
message = """
Never gonna give you up
Never gonna let you down
"""
print(message)
Output
Never gonna give you up Never gonna let you down
In the above example, anything inside the enclosing triple quotes is one multiline string.
Python String Operations
Many operations can be performed with strings, which makes it one of the most used data types in Python.
1. Compare Two Strings
We use the == operator to compare two strings. If two strings are equal, the operator returns True. Otherwise, it returns False. For example,
str1 = "Hello, world!"
str2 = "I love Swift."
str3 = "Hello, world!"
# compare str1 and str2
print(str1 == str2)
# compare str1 and str3
print(str1 == str3)
Output
False True
In the above example,
- str1 and str2 are not equal. Hence, the result is
False. - str1 and str3 are equal. Hence, the result is
True.
2. Join Two or More Strings
In Python, we can join (concatenate) two or more strings using the + operator.
greet = "Hello, "
name = "Jack"
# using + operator
result = greet + name
print(result)
# Output: Hello, Jack
In the above example, we have used the + operator to join two strings: greet and name.
Iterate Through a Python String
We can iterate through a string using a for loop. For example,
greet = 'Hello'
# iterating through greet string
for letter in greet:
print(letter)
Output
H e l l o
Python String Length
In Python, we use the len() method to find the length of a string. For example,
greet = 'Hello'
# count length of greet string
print(len(greet))
# Output: 5
String Membership Test
We can test if a substring exists within a string or not, using the keyword in.
print('a' in 'program') # True
print('at' not in 'battle') # False
Methods of Python String
Besides those mentioned above, there are various string methods present in Python. Here are some of those methods:
| Methods | Description |
|---|---|
| upper() | Converts the string to uppercase |
| lower() | Converts the string to lowercase |
| partition() | Returns a tuple |
| replace() | Replaces substring inside |
| find() | Returns the index of the first occurrence of substring |
| rstrip() | Removes trailing characters |
| split() | Splits string from left |
| startswith() | Checks if string starts with the specified string |
| isnumeric() | Checks numeric characters |
| index() | Returns index of substring |
Escape Sequences in Python
The escape sequence is used to escape some of the characters present inside a string.
Suppose we need to include both a double quote and a single quote inside a string,
example = "He said, "What's there?""
print(example) # throws error
Since strings are represented by single or double quotes, the compiler will treat "He said, " as a string. Hence, the above code will cause an error.
To solve this issue, we use the escape character \ in Python.
# escape double quotes
example = "He said, \"What's there?\""
# escape single quotes
example = 'He said, "What\'s there?"'
print(example)
# Output: He said, "What's there?"
Here is a list of all the escape sequences supported by Python.
| Escape Sequence | Description |
|---|---|
\\ |
Backslash |
\' |
Single quote |
\" |
Double quote |
\a |
ASCII Bell |
\b |
ASCII Backspace |
\f |
ASCII Formfeed |
\n |
ASCII Linefeed |
\r |
ASCII Carriage Return |
\t |
ASCII Horizontal Tab |
\v |
ASCII Vertical Tab |
\ooo |
Character with octal value ooo |
\xHH |
Character with hexadecimal value HH |
Python String Formatting (f-Strings)
Python f-Strings makes it easy to print values and variables. For example,
name = 'Cathy'
country = 'UK'
print(f'{name} is from {country}')
Output
Cathy is from UK
Here, f'{name} is from {country}' is an f-string.
This new formatting syntax is powerful and easy to use. From now on, we will use f-Strings to print strings and variables.
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