Python String Tutorial with Examples

Python String
Access values in string
String is immutable
Escape Characters
String operators
Methods

1. Python String

String is the most common type in Python, and you often have to work with them. Note that there is no character type in Python, a simple character is called as a string of length 1.

There are two ways to declare a string written on a line by using single quotes or double quotes.

str1 = "Hello Python"
str2 = 'Hello Python'

str3 = "I'm from Vietnam"

str4 = 'This is a "Cat"! '

If you want to write string on multiple lines using a pair of 3 single quotes.

str = """Hello World
     Hello Python"""

2. Access values in string

Python does not support character type, the character is considered as a string of length 1. The characters in string are indexed by starting index 0. You can access substrings via index.

stringExample.py

mystr = "This is text"

# --> h
print ("mystr[1] = ", mystr[1])

# --> is is t
print ("mystr[2,9] = ", mystr[2:9])

# --> s is text
print ("mystr[3:] = ", mystr[3:])

3. String is immutable

String is a special data type in Python, and it is immutable. Each string has an address stored on memory. All operations on strings create another object. For example, if you want to concatenate a string with another string, this action creates another string on memory.

== and is operator

Python uses the == operator to compare the values of two objects. And use the "is" operator to compare locations on memory.

compareObject.py

class Person(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age
    # Override __eq__ method
    def __eq__(self, other):
        return self.name == other.name and self.age == other.age

jack1 = Person('Jack', 23)
jack2 = Person('Jack', 23)

# Call to __eq__ method
print ("jack1 == jack2 ?", jack1 == jack2) # True
print ("jack1 is jack2 ?", jack1 is jack2) # False

See more:
Comparing and Sorting in Python

String is a special data type and is frequently used in Python applications. And so it has some features below:

If you declare two string type variable with the same value, they all will point to the actual string in memory.

Operators with strings will create new strings in memory.

compareString.py

str1 = "Hello Python"
str2 = "Hello Python"
str3 = "Hello " + "Python"

print ("str1 == str2? ", str1 == str2) # --> True 
print ("str1 is str2? ", str1 is str2) # --> True  
print ("str1 == str3? ", str1  == str3) # --> True 
print ("str1 is str3? ", str1 is str3) # --> False

4. Escape Characters

Escape characters are special characters in Python. It is non-printable characters. However if you want it to appear in your string, you need a notation to notify to Python. For example, "\n" is a newline character.

escapeCharacterExample.py

# Two "tab" characters between "Hello World" and "Hello Python".
mystr = "Hello World\t\tHello Python" 
print (mystr)

# Two "newline" characters between "Hello World" and "Hello Python".
mystr = "Hello World\n\nHello Python" 
print (mystr)

Output:

Hello World       Hello Python
Hello World

Hello Python

Backslash notation	Hexadecimal character	Description
\a	0x07	Bell or alert
\b	0x08	Backspace
\cx		Control-x
\C-x		Control-x
\e	0x1b	Escape
\f	0x0c	Formfeed
\M-\C-x		Meta-Control-x
\n	0x0a	Newline
\nnn		Octal notation, where n is in the range 0.7
\r	0x0d	Carriage return
\s	0x20	Space
\t	0x09	Tab
\v	0x0b	Vertical tab
\x		Character x
\xnn		Hexadecimal notation, where n is in the range 0.9, a.f, or A.F

5. String operators

In Python, there are some special operators below:

Operator	Description	Example
+	Concatenation - Adds values on either side of the operator	"Hello" +"Python" ==> "Hello Python"
*	Repetition - Creates new strings, concatenating multiple copies of the same string	"Hello"*2 ==> "HelloHello"
[]	Slice - Gives the character from the given index	a = "Hello" a[1] ==> "e"
[ : ]	Range Slice - Gives the characters from the given range	a = "Hello" a[1:4] ==> "ell" a[1: ] ==> "ello"
in	Membership - Returns true if a character exists in the given string	a = "Hello" 'H' in a ==> True
not in	Membership - Returns true if a character does not exist in the given string	a = "Hello" 'M' not in a ==> True
r/R	Raw String - Suppresses actual meaning of Escape characters. The syntax for raw strings is exactly the same as for normal strings with the exception of the "raw string operator", the letter "r," which precedes the quotation marks. The "r" can be lowercase (r) or uppercase (R) and must be placed immediately preceding the first quote mark.	print (r'\n\t') ==> \n\t print (R'\n\t') ==> \n\t
%	Format - Performs String formatting	See at next section

6. Methods

TODO