Keywords in Python: A Brief Introduction

Key takeaways

• There’s a new version always in development that comes with some improvements.
• keyword def In Python context managers are very supportive which can be used with the help of With keyword.
• To understand and execute the code, these keywords are used by python interpreter.

Python is a dynamic and evolving language. There’s a new version always in development that comes with some improvements. Python comes in various versions such as 1. X, 2. X and 3. X series.

As for Python keywords, they are reserved words which means they can’t be changed or used as a variable name, function name, dictionary name or as any other identifier.

Let’s jump to keywords that are supported by Python 2. X and Python 3. X.

Though there are several keywords that are similar in both functions, some keywords are specific to Python 2. X Python 3. X.

Original diagram for Techfastly by Vin Patel.

Keywords supported by Python 2. X #

Here is the table of keywords supported by Python 2. X.

Original diagram for Techfastly by Vin Patel.

Keywords supported by Python 3. X #

Here’s a table of keywords supported by Python 3. X.

Original diagram for Techfastly by Vin Patel.

Function of keywords #

Let’s discuss when and how these keywords are uses in programming.

Value keywords #

The False keyword #

Python offers something called the comparison operator which identifies “False” keywords, this occurs when all the condition don’t satisfy. The comparison operator also represents the “truth value” in Python which is the same as zero (0).

>>> x=5
>>> y=10
>>> x>y
False

keyword False

The True keyword #

This one is a Boolean value much like the False keyword. The result derives from comparison operation which is same as one (1).

>>> x=5
>>> y=10
>>> x>> def test_function(): 
>>>    print('Hello World')
>>> x= test_function()
>>> print(x) 

Hello World
None

keyword None

Operands keywords #

The And keyword #

The keyword And checks whether the left and right operands in boolean expression are True or not. If both satisfy the condition then it must return True otherwise it is False.

>>> True and False
False

keyword and

The Not keyword #

This keyword primarily inverts the result of conditional statement. First it finds the Boolean value i-e True or False, then it returns the result after flipping.

>>> not False
True

keyword not

The Or keyword #

The logical or operation returns True when at least one operand satisfies the given condition.

>>> True or False
True

keyword or

The Is keyword #

This keyword Is is used to check the identity of the object. The result doesn’t turn true for equal objects but only for exact objects in memory.

>>> True is True
True

keyword is

The In keyword #

It is membership operator. It checks if any specific member is the part of the container or not. The result is generally True or False.

>>> list=['Harry','John','Alice']
>>> 'Harry' in list
True

keyword in

Control flow keywords #

The If keyword #

For conditional statements we use keyword If which is mostly executed only when the condition If is true.

The Elf keyword #

This keyword is only used when we have an If statement. It is basically “Else If”. When the condition of If statement is False it continues with Elf block. We may have multiple Elf blocks in the code.

The Else keyword #

If the set condition for If and Elf blocks are False then the body of Else will be executed.

>>> def if_elif_else(x):
>>>    if x < 0:
>>>       print('x is negative')
>>>    elif x == 0:
>>>       print('x is zero')
>>>    else:
>>>       print('x is positive')
>>> if_elif_else(1)
>>> if_elif_else(-1)
>>> if_elif_else(0)

x is positive
x is negative
x is zero

keywords if, elf and else

Iteration keywords #

The for keyword #

In Python, we define loop by the keyword For. It iterates over items in a variable, list, tulle or dictionary.

>>> fruits = ["apple","banana","mango"]
>>> for x in fruits:
>>>   print(x)

apple
banana
mango

keyword for

The While keyword #

In python, while loop uses the keyword While. The loop continues to run the block till the expression that follows the While keyword is true.

The Break keyword #

We can use keyword Break in both for and while loop. It stops the execution of the current loop and moves to the next section which is immediately below the loop.

The Continue keyword #

Like the keyword Break, Continue also works for both loops i.e For loop and While loop.

It basically skips the current iteration and moves to the next one.

>>> i=0
>>> while True:
>>>    i += 1
>>>    if i>=5 and i<= 10:
>>>       continue # skip the next part
>>>    elif i == 15:
>>>       break #stop the loop
>>>     print(i)
1
2
3
4
11
12
13
14

Keywords while,continue and break

Structure keywords #

The Class keyword #

Python is Object Oriented Programming (OOP), a class which is used for describing one or more objects. This keyword helps to create a user defined class.

>>> class Person:
>>>   name ="Hannah"
>>>   age = 12

keyword class

The Def keyword #

It helps to define user-defined function or method of a class. The purpose of using functions is to organize our set of instructions.

>>> def my_function():
>>>   print("This is my function")
>>> my_function()

This is my function

keyword def

The With keyword #

In Python context managers are very supportive which can be used with the help of With keyword. The basic example is to with I/O files. It opens the specific file, manipulates, and closes it.

>>> with open('file_path','w') as file:
>>>    file.write('Hello World')

keyword with

The Pass keyword #

The pass statement (equivalent to null statement) in python does nothing. We use Pass when we need a statement but don’t want to run any code. Following are the few useful examples of using keyword pass.

>>> def my_function():
>>>     pass
    
>>> class My_Class:
>>>     pass
   
>>> if True:
>>>     pass

keyword pass

The Lambda keyword #

This keyword is used to create anonymous function (with no name). It has only one statement and no return statement.

>>> square =lambda x:x**2
>>> for item in range(5,10):
>>>    print(square(item))
25
36
49
64
81

keyword lambda

Returning keywords #

The return keyword #

The Return keyword is used only inside the body of a function (defined by using the keyword def). Whenever keyword return comes, the programmed will exit the function and nothing executes after it.

>>> def factorial(n):
>>>     if n==1:
>>>         return 1
>>>     else:
>>>         return n * factorial(n-1)
>>> factorial(4)

24

keyword return

The Yield keyword #

The Yield is similar to the Return keyword in the function. Just as keyword Return returns the result to the caller, the Yield returns a generator.

>>> def function_name():
>>>     yield "H"
>>>     yield "E"
>>>     yield "L"
>>>     yield "L"
>>>     yield "O"
>>> check = function_name()
>>> for i in check:
>>>     print(i)

H
E
L
L
O

keyword yield

Import Keywords #

The Import keyword #

When we need to import other modules in our programmed, we use the keyword. Import.

The From keyword #

It is used to import some specific variable, class or function from the module.

The As keyword #

This keyword helps us define another name for a module which mostly is imported.

In this case, we are importing the module factorial from Math which can also be called fac.

>>> from math import factorial as fac
>>> num = 5 
>>> # printing factorial 
>>> print("factorial of " , num , "is =" , fac(num))

factorial of 5 is = 120

keywords from, import and as

Exceptional handling keywords #

The Try keyword #

The errors which programmer can except during run time written in try block**.**

The Except keyword #

The keyword Except handles exception in the programmed. This function is executed when error occurs in the Try block. We can use more Except block with one try block.

The Finally keyword #

Whatever is in the Final block gets executed regardless an error occurs or not in the try block.

>>> try:
>>>    x = 3/0
>>>    print(x)
>>> except:
>>>    print("Something went wrong")
>>> else:
>>>    print("Nothing went wrong")
>>> finally:
>>>    print("Bye")

Something went wrong
Bye

keywords try, except and finally

The Raise keyword #

This keyword is used for raising our own errors in the programmed.

>>> if x<3:
>>>   raise Exception("Write number greater than three")

keyword raise

The Assert keyword #

If we are to confirm certain statements - that is to discover if it is true or not, then we use keyword Assert.

This keyword is used to insert debugging assertion in our programs. If the assertion becomes true it will run the programmed otherwise it raises an Assertion Error.

>>> val = 10
>>> assert val > 100

---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
 in ()
      1 val = 10
----> 2 assert val > 100

AssertionError:

keyword assert

Variable handling keywords #

The Del keyword #

Keyword Del is used to delete reference of objects in the programmed. Commonly, it is used to remove indexes from list or a dictionary.

>>> names = ["John","Tom"]
>>> del names[1]
>>> print(names)

['John']

keyword del

The Global keyword #

The Global keyword reads and modifies the global variable**.** It also pulls the variable from global scope into the function.

>>> x = "global"
>>> def function():
>>>     global x
>>>     x = x *2
>>>     print(x)
>>> function()

global global

keyword global

The Nonvocal keyword #

When working with the nested function, the variable which is defined in the outer function is not local to the inner function. So we can’t modify it without using the keyword nonvocal.

>>> def outer_function():
>>>     x = "local"
>>>     def inner_function():
>>>         nonlocal x
>>>         x = "nonlocal"
>>>         print("inner:",x)
>>>     inner_function()
>>>     print("outer:",x)
>>> outer_function()

inner: nonlocal
outer: nonlocal

keyword nonvocal

Keywords that become built_in function in 3. X series #

The Exec keyword #

This keyword executed the python code as a string.

>>> exec "x = 3* 7"
>>> x == 21

True

keyword exec

The print keyword #

This keyword is used to print anything to console.

>>> print "That's all about keywords.Hope you like it"

That's all about keywords.Hope you like it

keyword print

Conclusion #

In this tutorial we covered all the keywords supported by python 2. X and 3. X series and their uses. Keywords are like the building blocks in the game of python programming. Without using them, it’s not possible for us to write any code. All keywords have their own specific function. To understand and execute the code, these keywords are used by python interpreter.

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