Every language contains words and a set of rules that would make a sentence meaningful. Similarly, in Python programming language, there are a set of predefined words, called Keywords which along with Identifiers will form meaningful sentences when used together. Python keywords cannot be used as the names of variables, functions, and classes.
In this article, we will learn about Python keywords and identifiers and how to use them to perform some tasks.
Keywords in Python
Python Keywords are some predefined and reserved words in Python that have special meanings. Keywords are used to define the syntax of the coding. The keyword cannot be used as an identifier, function, or variable name. All the keywords in Python are written in lowercase except True and False. There are 35 keywords in Python 3.11.
In Python, there is an inbuilt keyword module that provides an iskeyword() function that can be used to check whether a given string is a valid keyword or not. Furthermore, we can check the name of the keywords in Python by using the kwlist attribute of the keyword module.
Rules for Keywords in Python
- Python keywords cannot be used as identifiers.
- All the keywords in Python should be in lowercase except True and False.
List of Python Keywords
|
Keywords |
Description |
|---|---|
| and | This is a logical operator which returns true if both the operands are true else returns false. |
| or | This is also a logical operator which returns true if anyone operand is true else returns false. |
| not | This is again a logical operator it returns True if the operand is false else returns false. |
| if | This is used to make a conditional statement. |
| elif | Elif is a condition statement used with an if statement. The elif statement is executed if the previous conditions were not true. |
| else | Else is used with if and elif conditional statements. The else block is executed if the given condition is not true. |
| for | This is used to create a loop. |
| while | This keyword is used to create a while loop. |
| break | This is used to terminate the loop. |
| as | This is used to create an alternative. |
| def | It helps us to define functions. |
| lambda | It is used to define the anonymous function. |
| pass | This is a null statement which means it will do nothing. |
| return | It will return a value and exit the function. |
| True | This is a boolean value. |
| False | This is also a boolean value. |
| try | It makes a try-except statement. |
| with | The with keyword is used to simplify exception handling. |
| assert | This function is used for debugging purposes. Usually used to check the correctness of code |
| class | It helps us to define a class. |
| continue | It continues to the next iteration of a loop |
| del | It deletes a reference to an object. |
| except | Used with exceptions, what to do when an exception occurs |
| finally | Finally is used with exceptions, a block of code that will be executed no matter if there is an exception or not. |
| from | It is used to import specific parts of any module. |
| global | This declares a global variable. |
| import | This is used to import a module. |
| in | It’s used to check whether a value is present in a list, range, tuple, etc. |
| is | This is used to check if the two variables are equal or not. |
| none | This is a special constant used to denote a null value or avoid. It’s important to remember, 0, any empty container(e.g empty list) do not compute to None |
| nonlocal | It’s declared a non-local variable. |
| raise | This raises an exception. |
| yield | It ends a function and returns a generator. |
| async | It is used to create asynchronous coroutine. |
| await | It releases the flow of control back to the event loop. |
The following code allows you to view the complete list of Python’s keywords.
This code imports the “keyword” module in Python and then prints a list of all the keywords in Python using the “kwlist” attribute of the “keyword” module. The “kwlist” attribute is a list of strings, where each string represents a keyword in Python. By printing this list, we can see all the keywords that are reserved in Python and cannot be used as identifiers.
Python3
# codeimport keywordprint(keyword.kwlist) |
['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is',...
Identifiers in Python
Identifier is a user-defined name given to a variable, function, class, module, etc. The identifier is a combination of character digits and an underscore. They are case-sensitive i.e., ‘num’ and ‘Num’ and ‘NUM’ are three different identifiers in python. It is a good programming practice to give meaningful names to identifiers to make the code understandable.
We can also use the Python string isidentifier() method to check whether a string is a valid identifier or not.
Rules for Naming Python Identifiers
- It cannot be a reserved python keyword.
- It should not contain white space.
- It can be a combination of A-Z, a-z, 0-9, or underscore.
- It should start with an alphabet character or an underscore ( _ ).
- It should not contain any special character other than an underscore ( _ ).
Examples of Python Identifiers
Valid identifiers:
- var1
- _var1
- _1_var
- var_1
Invalid Identifiers
- !var1
- 1var
- 1_var
- var#1
- var 1
Python Keywords and Identifiers Examples
Example 1: Example of and, or, not, True, False keywords.
Python
print("example of True, False, and, or, not keywords")# compare two operands using and operatorprint(True and True)# compare two operands using or operatorprint(True or False)# use of not operatorprint(not False) |
example of True, False, and, or, not keywords True True True
Example 2: Example of a break, continue keywords and identifier.
Python
# execute for loopfor i in range(1, 11): # print the value of i print(i) # check the value of i is less than 5 # if i lessthan 5 then continue loop if i < 5: continue # if i greater than 5 then break loop else: break |
1 2 3 4 5
Example 3: example of for, in, if, elif, and else keywords.
Python
# run for loopfor t in range(1, 5): # print one of t ==1 if t == 1: print('One') # print two if t ==2 elif t == 2: print('Two') else: print('else block execute') |
One Two else block execute else block execute
Example 4: Example of def, if, and else keywords.
Python
# define GFG() function using def keyworddef GFG(): i=20 # check i is odd or not # using if and else keyword if(i % 2 == 0): print("given number is even") else: print("given number is odd") # call GFG() function GFG() |
given number is even
Example 5: Example of try, except, raise.
Python
def fun(num): try: r = 1.0/num except: print('Exception raises') return return rprint(fun(10))print(fun(0)) |
0.1 Exception raises None
Example 6: Example of a lambda keyword.
Python
# define a anonymous using lambda keyword# this lambda function increment the value of ba = lambda b: b+1# run a for loopfor i in range(1, 6): print(a(i)) |
2 3 4 5 6
Example 7: use of return keyword.
Python
# define a functiondef fun(): # declare a variable a = 5 # return the value of a return a# call fun method and store# it's return value in a variable t = fun()# print the value of tprint(t) |
5
Example 8: use of a del keyword.
Python
# create a listl = ['a', 'b', 'c', 'd', 'e']# print list before using del keywordprint(l)del l[2]# print list after using del keywordprint(l) |
['a', 'b', 'c', 'd', 'e'] ['a', 'b', 'd', 'e']
Example 9: use of global keyword.
Python
# declare a variablegvar = 10# create a functiondef fun1(): # print the value of gvar print(gvar)# declare fun2()def fun2(): # declare global value gvar global gvar gvar = 100# call fun1()fun1()# call fun2()fun2() |
10
Example 10: example of yield keyword.
Python
def Generator(): for i in range(6): yield i+1t = Generator()for i in t: print(i) |
1 2 3 4 5 6
Example 11: Use of assert keyword.
Python3
def sumOfMoney(money): assert len(money) != 0,"List is empty." return sum(money)money = []print("sum of money:",sumOfMoney(money)) |
Output:
AssertionError: List is empty.
Example 12: Use of pass keyword
Python3
class GFG: passg = GFG |
Example 13: Use of finally keyword
Python3
def divide(a, b): try: c = a/b print("Inside try block") except: print("Inside Exception block") finally: print("Inside finally block")divide(3,2)divide(3,0) |
Inside try block Inside finally block Inside Exception block Inside finally block
Example 14: Use of import keyword
Python3
import mathprint("factorial of 5 is :", math.factorial(5)) |
factorial of 5 is : 120
Example 15: Use of is keyword
Python3
x = 10y = 20z = xprint(x is z)print(x is y) |
True False
Example 16: Use of from keyword
Python3
from math import gcdprint("gcd of 345 and 675 is : ", gcd(345, 675)) |
gcd of 345 and 675 is : 15
Example 17: Use of async and await keyword
Python3
# codeimport asyncioasync def factorial(n): if n == 0: return 1 return n * await factorial(n - 1)def main(): result = asyncio.run(factorial(5)) print(result)if __name__ == "__main__": main() |
120
The async and await keywords make it easy to write asynchronous code in Python. They allow you to write code that runs concurrently with other tasks, which can improve the performance of your programs.
This program defines two functions: factorial() and main(). The factorial() function is an asynchronous function, which means it can run concurrently with other tasks. The await keyword is used to suspend the execution of the factorial() function until it completes. The main() function simply calls the factorial() function and prints the result.
FAQs on Python Keywords and Identifiers
Q: What are Keywords and Identifiers in Python?
Answer: Keywords in Python are predefined words that have a special meaning to the interpreter. They are reserved words that are used to perform a specific task in Python programming.
Identifiers in Python are names given to different parts of a Python program like variables, functions, classes, etc. They are user-defined and the users must follow a set of rules to define them in a python program.
Q: What is the difference between a Keyword and an Identifier in Python?
Answer: A Keyword in Python is a predefined reserved word that is meaningful to the interpreter and performs a specific task. Whereas, an identifier is a userdefined word given to different parts of python programming. An identifier can be a name given to a variable, function or a class.
