Operators, Control Flow, and Functions in Python - Python Basics Masterclass Continued

In the last article, we studied what is python, how to install it on your computer, and basic data types in python(numeric, strings, lists, tuples, dictionaries). In this article, we will study operators in python, control flow statements and functions in python.

Operators in Python

An operator is a specific symbol that is used to perform some sort of arithmetic or logical operation. An operational statement contains two parts operand and operator. The variables that will be changed after the operation are called operands and the symbol used is called operator.

Let’s understand the concept of operands and operator by an example:

a = b + c

Here a, b, and c are operands as they are the elements that will be operated, and (=, +) are operators as they will be used to change the value of a by adding b to c.

Now let’s understand the types of operators in python

Arithmetic Operators

Assignment Operators

As the name suggests these operators are used to perform assignment operation on the variable

Comparison Operators

These operators are used to compare the values of left and right operands.

Bitwise Operators

These operators are used to directly manipulate the bits of the value of operands.

Logical Operators

These are used to check a certain kind of logic from both of the operands.

• and (True if both left and right operands are true)
• or (True if either one operand is true)
• not (Gives the opposite of the operand passed)

a = True
b = False
print(a and b, a or b, not a)

Membership Operators

These are used to test whether a particular variable or value exists in either a list, dictionary, tuple, set and so on.

The operators are :

• in (True if the value or variable is found in the sequence)
• not in (True if the value is not found in the sequence)

a = [1, 2, 3, 4]
if 5 in a:
    print('Yes!')
if 5 not in a:
    print('No!') 
# Output: No!

Identity Operator

These operators are used to check whether the values, variables are identical or not. As simple as that.

The operators are :

• is (True if they are identical)
• is not (True if they are not identical)

a = 5
b = 5
if a is b:
    print('Similar')
if a is not b:
    print('Not Similar!')
# Output: Similar

Flow Control in Python

There are 3 types of flow control statement/blocks in python.

• Sequential - Normal code block which executes line by line
• Selection / Decision Making (Conditional) - Statements are executed after a decision is made based on some condition.
• Repetition - Same statements are repeated

Conditional Statements

Conditional statements are executed only if a certain condition is met, else it is skipped ahead to where the condition is satisfied. Conditional statements in Python are the if, elif and else.

Syntax:

if condition:
    statement
elif condition:
    statement
else:
    statement

This means that if a condition is met, do something. Else go through the remaining elif conditions and finally if no condition is met, execute the else block. You can even have nested if-else statements inside the if-else blocks.

a = 10
b = 15
if a == b:
    print ( 'They are equal' )
elif a > b:
    print ( 'a is larger' )
else :
    print ( 'b is larger' )
# Output: b is larger

Repetitive Statements(Looping)

You have 2 kinds of loops in Python:

• for
• while

For Loop:

These loops are used to perform a certain set of statements for a given condition and continue until the condition has failed. Syntax

for variable in range: statements

Example

basket_of_fruits= ['apple', 'orange', 'pineapple', 'banana']
for fruit in basket_of_fruits:
    print(fruit, end=',')

While Loops:

While loops are the same as the for loops with the exception that you may not know the ending condition.

Syntax

while condition:
    statements

Example

seconds = 10
while seconds >= 0:
    print(seconds, end='->')
    second-=1
print("Boom")

Functions in Python

A function is a block of code in python which gets executed when a function itself is being called.

Functions work on the principle of “Don’t repeat yourself (DRY)”, you write the block of code once within the function and that code block can be used again by just calling the function(instead of writing the same code again and again).

Syntax

In python, a function can be created using the def keyword.

def function_name([ arguments ]):
    statements
    [ return value ]

Example

To call a function, use the function name followed by parentheses.

def my_function():
    print("Hello I am being called")
my_function()
# Output: Hello I am being called

Function Arguments

Gif by tenor

Function arguments are not the same as our regular arguments😁. In terms of python programming, arguments are information passed to the function. Arguments are specified after the function name inside the parentheses.  You can argue as much as you want to. (Just kidding: I meant you can add as many arguments as you want to, just separate them with a comma).

The following example has a function with two arguments (first_name, last_name). When the function is called, we pass along a first name and last name, which is used inside the function to print the full name:

def print_name(first_name, last_name):
    print(first_name, last_name)
print_name("Dev", "Mehta")
print_name("Meet", "Parekh")
# Output: Dev Mehta
#         Meet Parekh

If you try to call the function with 1 or 3 arguments, you will get an error:

print_name("Dev")
# TypeError: print_name() missing 1 required
# positional argument: 'last_name'

Arbitrary Arguments or *args

If you do not know how many arguments will be passed into your function, add a * before the parameter name in the function definition.

This way the function will receive a tuple of arguments, and can access the items accordingly:

def youngest_kid(*kids):
  print("The youngest child is " + kids[2])
 
youngest_kid("Tanmay", "Haard", "Stavan") 
# Output: Stavan

Keyword Arguments

You can also send arguments with the key = value syntax. This way the order of the arguments does not matter.

def youngest_kid(child3, child2, child1):
  print("The youngest child is " + child3)
 
youngest_kid(child1 = "Haard", child2 = "Tanmay", child3 = "Stavan")
# Output: Stavan

Arbitrary Keyword Arguments or **kwargs

If you do not know how many keyword arguments will be passed into your function, add two asterisks: ** before the parameter name in the function definition.

This way the function will receive a dictionary of arguments, and can access the items accordingly:

Example

If the number of keyword arguments is unknown, add a double ** before the parameter name:

def get_last_name(**kid):
  print("His last name is " + kid["lname"])
 
get_last_name(fname = "Tanmay", lname = "Trivedi")
# Output: Trivedi

Function Return Values

To let a function return a value, use the return keyword:

def square(x):
    return x * x

Conclusion

 Gifs by tenor

In this article, we learned about what are operators, control flow and functions in python. If you want to learn what are the basics of python, you can read this previous article. In the next article, we will learn the name scoping in python and file handling in python. Until then, happy coding or you can read my other articles.