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 PythonPython 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 PythonKeywords
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.
Python
# code
import keyword
print(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 IdentifiersPython Keywords and Identifiers ExamplesValid identifiers:
- var1
- _var1
- _1_var
- var_1
Invalid Identifiers
- !var1
- 1var
- 1_var
- var#1
- var 1
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 operator
print(True and True)
# compare two operands using or operator
print(True or False)
# use of not operator
print(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 loop
for 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
Example 3: example of for, in, if, elif, and else keywords.
Python
# run for loop
for 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 keyword
def 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 r
print(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 b
a = lambda b: b+1
# run a for loop
for i in range(1, 6):
print(a(i))
Example 7: use of return keyword.
Python
# define a function
def 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 t
print(t)
Example 8: use of a del keyword.
Python
# create a list
l = ['a', 'b', 'c', 'd', 'e']
# print list before using del keyword
print(l)
del l[2]
# print list after using del keyword
print(l)
['a', 'b', 'c', 'd', 'e'] ['a', 'b', 'd', 'e']
Example 9: use of global keyword.
Python
# declare a variable
gvar = 10
# create a function
def 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()
Example 10: example of yield keyword.
Python
def Generator():
for i in range(6):
yield i+1
t = Generator()
for i in t:
print(i)
Example 11: Use of assert keyword.
Python
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
PythonExample 13: Use of finally keyword
Python
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
Python
import math
print("factorial of 5 is :", math.factorial(5))
factorial of 5 is : 120
Example 15: Use of is keyword
Python
x = 10
y = 20
z = x
print(x is z)
print(x is y)
Example 16: Use of from keyword
Python
from math import gcd
print("gcd of 345 and 675 is : ", gcd(345, 675))
gcd of 345 and 675 is : 15
Example 17: Use of async and await keyword
Python
# code
import asyncio
async 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()
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.
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4