Python Keywords with Examples
|In this Python article, we will discuss the python keywords by implementing them with the example.
Keywords are the pre-defined word having special meaning to the language compiler. These keywords can not be used for anything other than that special purpose.
and | as | assert |
break | class | continue |
elif | del | def |
else | except | False |
finally | for | from |
global | if | import |
lambda | is | in |
None | nonlocal | not |
or | pass | raise |
return | True | try |
while | with | yield |
__peg_parser__ | await | async |
Let’s see how we can use these Keywords in Python
1. and, or, not, True, False, is
and, or, not
are logical operators which after comparing the operands return a boolean value i.e. either True or False.
is
keyword is an identity operator which is used to check if two values reside in the same memory location or not.
# and returns true if both the operands are true else it returns false print(True and False) # or returns true if any of the operands are true else it returns false print(True or False) # not returns the opposite True--> False False--> True print(not(True)) print(type(2) is int)
Output False True False True
2. if, elif, else, for, in
if, elif, else
are conditional statements that choose the set of statements for execution, depending on the expression’s return value.
for
is used to perform a set of instructions repeatedly until a certain condition is fulfilled.
in
checks if the element is present or not in the list, tuple, or in a particular range, etc.
for i in range(10): if i % 2 == 0: # true is number is divisible by 2 print(i, "is a multiple of 2") elif i % 3 == 0: # true is number is divisible by 2 print(i, "is a multiple of 3") else: # true is number is not divissiblee by 2 nor by 3 print(i, "is not a multiple of either 2 or 3")
Output 0 is a multiple of 2 1 is not a multiple of either 2 or 3 2 is a multiple of 2 3 is a multiple of 3 4 is a multiple of 2 5 is not a multiple of either 2 or 3 6 is a multiple of 2 7 is not a multiple of either 2 or 3 8 is a multiple of 2 9 is a multiple of 3
3. while, pass, break, continue
while
loop iterates until a condition is true.
break
statement enables a program to skip over a part of the code by forcing the termination of a loop.
continue
statement also skip over a part of the code but instead of forcing the termination of the loop, it forces the next iteration of the loop to take place and skips the current one.
pass
statement does nothing. The interpreter does not ignore this statement but since it is a null statement there is no output. So when we don’t want to do anything, or we want to implement a method in the future we use pass
statement, otherwise we will get an error.
count = 1 while True: if count % 2 == 0: # only increment if multiple of 2 count += 1 continue elif count % 3 == 0: # if count is a multiple of 3 then don't do anything pass else: print(count) if count > 10: # if count is greater than 10 break the loop break else: count += 1
Output 1 5 7 11
4. from, import, as
import
is used to use an external source file or module in our current source file.
Whenever we want to import only a specific function from a module we use from
as
keyword is used to create an alias or you can say another name .
Syntax :from
module_nameimport
function/module name
For learning more about from and import, check the python article on modules.
from datetime import datetime as dt print(dt.now())
Output 2021-02-17 18:57:51.183834
5. try, except, finally, raise
If inside the try
block we will get an error then it will directly be caught by the except block. As soon as we get the error nothing will be executed after that line and the compiler will directly go to the except block.
Finally
block always gets compiled, it does not matter if try
throws an error or not.
In the below example the try block will throw a ZeroDivisionError and except will catch that.
raise
keyword is used to throw an exception intentionally.
try: print("working inside try block") l = 20 / 0 print("This line will not print") except: print("Caught the exception") finally: print("It Always print with or without error") if True: raise Exception("Raising an exception")
Output working inside try block Caught the exception It Always print with or without error Traceback (most recent call last): File "c:\Users\parih\Desktop\testing.py", line 14, in <module> raise Exception("Raising an exception") Exception: Raising an exception
6. def, return, yield, None
def
keyword is used to define a function in python. Functions serve two main purposes. The first is to encapsulate a code block and give a meaningful descriptive name to it so that it makes the code clean and easy to read. And the second use is reusability i.e. whenever we need a code, again and again, we use a function instead of writing the code multiple times.
return
is used to return some value from the function .
yield
is the same as a return but instead of returning just the value, it returns a generator.
None
keyword is as no value. None is its own data type it is not equal to 0 or False
def test_for_return(): return "Codingeek" def test_for_yield(): yield "Codingeek" def test_for_none(): return None print("return value : ", test_for_return()) print("return type : ", type(test_for_return())) print("yield keyword : ", test_for_yield()) print("yield type : ", type(test_for_yield())) print("None Keyword : ", test_for_none()) print("None type : ", type(test_for_none()))
Output return value : Codingeek return type : <class 'str'> yield keyword : <generator object test_for_yield at 0x000001FA45B0AC10> yield type : <class 'generator'> None Keyword : None None type : <class 'NoneType'>
7. assert
assert
keyword is mainly used in testing, if the input condition returns true then it does not do anything otherwise it will throw an AssertionError.
assert 10 % 2 == 0, "Not Divisible by 2" b = 0 assert b != 0, "ZeroDivisionError" print(20 / b)
Output Traceback (most recent call last): File "c:\Users\parih\Desktop\testing.py", line 3, in <module> assert b!=0,"ZeroDivisionError" AssertionError: ZeroDivisionError
8. class, del
Python Classes are a way to bind attributes and methods, simply we can say the class is used to bind related variables and function together in a logical entity that can be instantiated and used repeatedly in the code. Classes are basically the blueprint of the object and the instantiated value is known as an Object.
Read More: Classes and Objects
In python we define a class using class
keyword.
The del
keyword is used to delete an object but everything in python is an object so we using del we can delete anything like variables, list, tuple, classes etc.
class Dialogue: name = "Codingeek" def say(self): print("It's a beautiful day to save lives") x = Dialogue() print(x.name) x.say() print(Dialogue) del Dialogue print(Dialogue)
Output Codingeek It's a beautiful day to save lives <class '__main__.Dialogue'> Traceback (most recent call last): File "c:\Users\parih\Desktop\testing.py", line 11, in <module> print(Dialogue) NameError: name 'Dialogue' is not defined
9. global, nonlocal
global
keyword in Python is used to create a global variable from the no-scope area, for example: inside a function, inside a loop, etc.
the non-local
keyword is similar to a global keyword but it is mostly used in the nested function so that the variable modification inside the nested function does not get destroyed in the outer function.
def func1(): x = "Website" def func2(): nonlocal x x = "Codingeek" def func3(): x = "Working" global y y = "It's global" func2() func3() return x print(func1()) print(y)
Output Codingeek It's global
10. lambda
lambda
keyword is used to create a small function, it can take any number of arguments but can have only one expression.
func = lambda x, y, z, l: (x + y + z) * l print(func(1, 2, 5, 5)) # (1 + 2 + 5) * 5
Output 40
11. with
with
keyword in Python is basically used in file handling and simplifies the exception handling because it does the clean-up task after the processing is completed. For example, it automatically closes the file once the with block is executed completely.
with open('output.txt', 'w') as f: f.write('Codingeek')
12. await, async,__peg_parser__
await
keywords suspend the execution of coroutine on an awaitable object. It can only be used inside a coroutine function.
To define a function coroutine we use the async
keyword. Functions defined with “async def” syntax are always coroutine functions, even if they do not contain “await
” or “async
” keywords.
The async
is similar to synchronized keyword in java.
For example:
async def func(param1, param2): do_stuff() await some_coroutine()
__peg_parser
is an Easter egg. It is a new keyword in Python 3.9. The __new_parser__ was renamed to __peg_parser__ recently.
help> __peg_parser__ no documentation found for '__peg_parser__' >>> __peg_parser__ SyntaxError: You found it!
13. Conclusion
In this article, we discussed all Python keywords and how to implement them in python.
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