String is a data type in python, which is used to handle array of characters. python strings are immutable. String is a sequence of Unicode characters that may be a combination of letters, numbers, or special symbols enclosed within single, double or even triple quotes. Python treats single quotes the same as double quotes and triple quotes.
Note: Python does not support a character type, they treat it as string.
Creating String
We can create a string by enclosing single quotes or double quotes or even triple quotes. String in single quotes cannot hold any other single quoted character in it, because the compiler will not recognize where to start and end the string. To overcome this problem, you have to use double quotes. Strings which contains double quotes should be define within triple quotes. Defining strings within triple quotes also allows creation of multiline strings.
Example:
#Using Single quotes
a = 'Neural Beast'
#Using Double quotes
b = "Neural Beast"
#Using Triple quotes
c = """Neural Beast"""
print(type(a))
print(type(b))
print(type(c))
Output:
<class 'str'>
<class 'str'>
<class 'str'>
Accessing characters
Square brackets along with index number can be used to access characters of the string. The indexing in python string starts from 0 for first element and n-1 for the last element, where n is the number of characters in the string.
Example:
a = "Neural Beast"
print(a[2])
Output:
u
String slicing
To access range of characters in a string we use slicing method, it is done using colon(:). The syntax is “str(start : end)“.
Example:
a = "Neural Beast"
print(a[0:6])
Output:
Neural
Deleting or Updating string
We cannot update or delete a character in a string. Strings are immutable, hence elements of a String cannot be changed once it has been assigned. If we try to delete or update a character in a string it will throw an error.
Example:
a = "Neural Beast"
a[0] = "R"
print(a)
Output:
Traceback (most recent call last):
File "string1.py", line 2, in <module>
a[0] = "R"
TypeError: 'str' object does not support item assignment
Update Entire String
We can assign a new string content in the existing variable as specified in the following example.
Example:
my_str = "Neural beast"
print(my_str)
my_str = "Hello Python"
print(my_str)
Output:
Neural beast
Hello Python
Replace string
We can replace a string with another string using replace() method.
Example:
my_str = "Hello Python"
print(my_str.replace("H", "F"))
Output:
Fello Python
Deleting the String
We can delete entire string using del keyword, but we cannot delete or remove a character in a string.
Example:
my_str = "Hello Python"
del my_str
print(my_str)
Output:
Traceback (most recent call last):
File "string1.py", line 3, in <module>
print(my_str)
NameError: name 'my_str' is not defined
Python Strings Operators
Python provies three types of operators. They are,
- Basic Operator
- Membership Operator
- Relational Operator
Basic Operator
There are two types of basic operators in python string.
- “+” is known as concatenation operator, it is used to join two strings.
- “*” is known as Replication Operator, it concatenates the multiple copies of the same string.
Example:
#concatenate two strings
a = "Neural"
b = "Beast"
c = a + b
print(c)
#Replication of strings
a = "Neural Beast\n"
print(a*4)
Output:
#concatenate two strings
NeuralBeast
#Replication of strings
Neural Beast
Neural Beast
Neural Beast
Neural Beast
Membership Operator
There are two membership operators in python string. They are,
in operator:
This operator returns true if a character or the entire substring exists in the given string, otherwise it returns false.
Example:
a = "Neural Beast"
b = "Hello Python"
c = "Python"
print("N" in a)
print("Hello" in b)
print(c in b)
Output:
True
True
True
not in operator
It returns true if a character the entire substring does not exist in the given string. otherwise it returns false.
Example:
b = "Hello Python"
c = "Neural beast"
print(c not in b)
Output:
True
Relational Operator
We ca use all the comparison operators in string. The string are compared based on the ASCII value or Unicode.
Example:
a = "Hello World"
b = "Neural beast"
print(a < b)
print(a != b)
Output:
True
True
Strings Formatting
The string formatting operator is one of the most exciting feature of python. The formatting operator % is used to construct strings, replacing parts of the strings with the data stored in variables.
Example:
a = "Python"
b = "Tutorial"
print("Welcome to our %s programming %s" %(a, b))
Output:
Welcome to our Python programming Tutorial
format() method
We can also use format() method for formatting strings. It contains curly brackets as placeholders which can hold arguments.
Example:
a = "Python"
b = "Tutorial"
print("Welcome to our {0} programming {1}".format(a, b))
print("{n} {b} ".format(n = 'Neural', b = 'Beast'))
Output:
Welcome to our Python programming Tutorial
Neural Beast
String Formatting Character
Format characters | Usage |
%c | character |
%d (or)%i | signed decimal integer |
%s | string |
%u | unsigned decimal integer |
%o | octal integer |
%x(or)%X | hexadecimal integer(lower case x refers a-f; upper case X refers A-F ) |
%e(or)%E | exponential notation |
%f | floating point numbers |
%g(or)%G | short numbers in floating point or exponential notation. |
Escape Character
Escape sequence starts with a backslash and it can be interpreted differently. When you have use single quote to represent a string, all the single quotes inside the string must be escaped. Similar is the case with double quotes.
Example:
# using single quotes
print('Neural Beast, " – Always deliver more than expected"')
# using double quotes
print("Neural Beast, \"– Always deliver more than expected\"")
# using triple quotes
print('''''Neural Beast, "– Always deliver more than expected"''')
Output:
Neural Beast, " – Always deliver more than expected"
Neural Beast, "– Always deliver more than expected"
''Neural Beast, "– Always deliver more than expected"
List Escape Sequences
Escape sequence | description |
\a | ASCII bell |
\b | ASCII backspace |
\f | ASCII form feed |
\n | ASCII linefeed |
\r | ASCII carriage return |
\t | ASCII horizontal tab |
\v | ASCII vertical tab |
\000 | Character with octal value000 |
\Xhh | Character with hexadecimal value HH |
String Methods in Python
capitalize() method
capitalize() method will return a copy of the string with its first character as capital and others letters in lowercase.
Example:
str1 = "welcome to python tutorial"
print(str1.capitalize())
str2 = "WElCOME TO PYTHON TUTORIAL"
print(str2.capitalize())
Output:
Welcome to python tutorial
Welcome to python tutorial
swapcase() method
swapcase() method will return a copy of string by converting uppercase characters to lowercase and lowercase characters to uppercase.
Example:
str1 = "Welcome To Python Tutorial"
print(str1.swapcase())
str2 = "wElCOME tO pYTHON tUTORIAL"
print(str2.swapcase())
Output:
wELCOME tO pYTHON tUTORIAL
WeLcome To Python Tutorial
upper() method
upper() method will return a copy of string in uppercase.
Example:
str1 = "welcome to python tutorial"
print(str1.upper())
Output:
WELCOME TO PYTHON TUTORIAL
lower() method
lower() method will return a copy of string in lowercase.
Example:
str1 = "WElCOME TO PYTHON TUTORIAL"
print(str1.lower())
Output:
welcome to python tutorial
startswith() method
startswith() method will return True if the string starts with the specific value.
Syntax:
str.startswith(value, start, end)
Example:
str1 = "welcome to python tutorial"
print(str1.startswith("we"))
str2 = "Hello Python"
print(str2.startswith("ll", 2, 4))
Output:
True
True
endswith() method
endswith() method will return True if the string ends with specific value.
Output:
str1 = "welcome to python tutorial"
print(str1.endswith("al"))
str2 = "Hello Python"
print(str2.startswith("lo", 3, 5))
Output:
True
True
Other String Methods
Function | Description |
Capitalize() | converts first character to capital letter |
Casefold() | converts to casefolded strings |
Center() | pads string with specified character |
Count() | returns occurrences of substring in string |
Encode() | returns encoded string of given string |
Endswith() | checks if string ends with the specified suffix |
Expandtabs() | returns tab character with spaces |
Find() | returns index of substring |
Format() | formats the string using dictionary |
Format_map() | formats the string using dictionary |
Index() | returns index of substring |
Input() | reads and returns a line of string |
Int() | returns integer from a number or string |
Isalnum() | checks alphanumeric character |
Isalpha() | checks if all characters are alphabets |
Isdecimal() | checks decimal characters |
Isdigit() | checks digit characters |
Isidentifier() | checks for valid identifiers |
Islower() | checks if all alphabets in a string are lowercase |
Isnumeric() | checks numeric characters |
Isprintable() | checks printable characters |
Isspace() | checks whitespace characters |
Istitle() | checks for titlecased string |
Isupper() | returns if all characters are uppercase characters |
Join() | returns s concatenated string |
Ljust() | returns left _ justified string of given width |
Lower() | returns lowercased string |
Lstrip() | removes leading characters |
Maketrans() | returns a translation table |
Partition() | returns a tuple |
Replace() | replaces substring inside |
Rfind() | returns the highest index of substring |
Rindex() | returns highest index of substring |
Rjust() | returns right-justified string of given width |
Rpartition() | returns a tuple |
Rsplit() | splits string from right |
Rstrip() | removes trailing characters |
Slice() | creates a slice object specified by range() |
Split() | splits string from left |
Splitlines() | splits string at line boundaries |
Startswith() | checks if string starts with the specified string |
Strip() | removes both leading and trailing characters |
Swapcase() | swap uppercase characters to lowercase; vice versa |
Title() | returns a title cased string |
Translate() | returns mapped character string |
Upper() | returns uppercased string |
Zfill() | returns a copy of the string padded with zeros |
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