What are Operators and Expressions in Python

Operators and Expressions in Python

Mathematics is the foundation for computers. Computers make mathematics accessible and programmable for complex systems such as Rocket Science. What do you think we do when we try to solve complex problems? Mathematics is all about equations and formulas to do something with the numbers. These numbers are called operands, and the activity that happens on them is operations. These operations consist of addition, subtraction, multiplication, division, exponentiation, modulus and many more scientific complex calculations. The symbols representing these operations are called operators, and the equations and formulas are called expressions in programming terminology. All operands can be considered as data or information on which we perform operations through the operators. In this blog, I will discuss these operators and expressions in detail to unfold the underlying programming concepts.

Overview of Operators

Operators and expressions are fundamental concepts in programming that allow us to perform various operations on data. All programming languages have this basic concept. We are discussing this from the perspective of Python Programming. It has several operators, and each one serves a specific purpose. I assume you know that in mathematics, expressions are evaluated in a particular order of operators when there is more than one operator in the expression—The Operator Precedence. Therefore, understanding operators and their precedence is crucial for writing error-free code. Before that, let's explore the different types of operators. Later, we will quickly go through their precedence and how to evaluate expressions effectively.

First things first, Python supports various types of operators. Below are the main categories:

• Arithmetic Operators
• Assignment Operators
• Comparison/Relational Operators
• Boolean Operators
• Bitwise Operators
• Bitwise Assignment Operators
• Conditional Operator
• Identity Operator
• Membership Operator
• Deletion Operator
• Callables Operators
• Bitwise Assignment Operators
• String Sequence Operators
• Sequence Assignment Operators
• Misc Operators

Let's see them one at a time, starting with Arithmetic Operators so that you can understand them better and more in-depth.

Arithmetic Operators

Python Arithmetic operations are given below with their respective Python operator symbol.

The names are self-explanatory. We don't need to discuss them in detail. Let's quickly see their precedence rules. The highest will be the first, and the lowest will be the last.

Precedence of Arithmetic Operators:

1. Exponentiation **
2. Unary plus + and unary minus -
3. Multiplication *, division /, and modulus %
4. Addition + and subtraction -

Assignment Operators:

Assignment operators are those where we assign some value directly or by evaluating expressions on the right-hand side to the left-hand side, usually a variable. The Python assignment operators with respective symbols and examples are below. Please go through them and try to use them in your programs. Assignment operators have the lowest precedence as it is the final step after expression evaluation is completed.

Relational Operators

Comparison operators are used to compare two values/operands. These values can be numbers, strings, booleans, and more. Generally, the LHS side is compared to the RHS with any of the operators below.

Python is amazing. You can also chain the comparison operators to depict exactly what is denoted in mathematics below. In mathematics, we see the below constraints many times.

0 < i < 100

-100 < n < 100

We can do the same check easily in Python like below:

if 0 < i < 100:
    print("i - Within Constraints")

if -100 < i < 100:
    print("i - Within Constraints")

You can test the above on your machine and let me know in the comments if this works or if I am wrong.

Boolean Operators

Many times, we have options in life to choose from. Imagine a situation in which you want to purchase a dress for yourself. Before buying the dress from the shop, you first decide what dress you want. Am I right? This time, you think of colours, styles, etc. So you choose from red OR blue. So, this OR is a logical operator. Similarly, you also use AND and NOT, do you? Below are Python's logical operators.

Bitwise Operators

These operators are called bitwise operators because they operate on bits. I assume that you know what bits are in machine code. Below are Python's bitwise operators.

Bitwise Assignment Operators

Conditional Operator - if else

if else is handy when you want to write condition-based assignments. See the below example.

is_email_valid = True if check_email(email) else False

print('Email is valid' if is_email_valid else "Email is invalid")

Identity Operator - is

It's a saviour when you quickly want to identify whether an object is identical to another. It returns True if the objects are the same. See the example below.

a = "This is test string 1"
b = "This is test string 1"
c = a

if a is b:
    print("a is b")
else:
    print("a is not b")
# Output
# a is not b

if c is a:
    print("c is a")
else:
    print("c is not a")
# Output
# c is b

Here, you can observe that it is entirely different from the comparison or relational operators. Behind the scenes, this operator looks for the variable's memory location instead of the value itself. Therefore, the First comparison between a and b is False and displayed - "a is not b". On line number 3, we created the Third variable c and assigned a to it. It did not copy the value of a but stored the memory location of a. Hence, the condition c is a gave True.

Clearly, the identity operator compares the memory location, whereas relational/comparison operators compare actual values.

Membership Operator - in

The membership operator checks whether the LHS operand exists in the collection or an iterable, such as a list or dictionary and returns a boolean. See the below example.

my_list = ["value1", 4, "v", 10.5]
item1 = "v"
item2 = 10.5
item3 = "10.5"

if item1 in my_list:
    print(item1, "exists")
else:
    print(item1, "does not exist")
#Output - v exists

if item2 in my_list:
    print(item2, "exists")
else:
    print(item2, "does not exist")
#Output - 10.5 exists

if item3 in my_list:
    print(item3, "exists")
else:
    print(item3, "does not exist")
#Output - 10.5 does not exist

You can test this code and let me know in the comments why the third condition was evaluated to "False" and printed "10.5 does not exist"

Deletion Operator - del

This operator deletes the object when you call it, like in the example below. You can delete a variable, dictionary item, list item, etc.

b = "This is test string 1"

print("b=", b)
del b
print("b=", b)
# Output
#Traceback (most recent call last):
#  File "", line 1, in 
#NameError: name 'b' is not defined

What if we use the previous example and try to delete c variable? Let's check it out.

a = "This is test string 1"
c = a

print("c=", c)
del c
print("a=", a)
print("c=", c)
# Output
#Traceback (most recent call last):
#  File "", line 1, in 
#NameError: name 'c' is not defined

Callables Operators

This is fascinating and useful when you want to pack/unpack the collections. Python modules and libraries use these extensively. Below is the list. Let's dig into it.

If you want to see examples, please visit the functions in Python blog, where I have explained this with examples.

String and Sequence Operators

This is intriguing because you can present the output to the console precisely as you wish so the user can follow it better and understand it quickly. Do you want to see the dictionary example? Look at this.

my_dict = {
    "language": "Python",
    "number": 2
}
print("%(language)s has %(number)03d quote types."  % my_dict)
# Output - Python has 002 quote types.

Sequence Assignment Operators

That's it for all operators Python supports. This is a huge list, isn't it? Now that you have seen all the operators, you can proceed with the precedence of operators. Wait a minute. Before you know the precedence of operators, you must understand the grouping operators. See the below:

The expression ((a + (b*c) / e)/d) has several groups, including inner groups. By thumb rule, the innermost group has to be evaluated first and so on. Let's understand this by an example.

a = 15
b = 14.7
c = -13
d = 12
e = 11
# Expression to evaluate with groups
ans = ((a + (b*c) / e)/d)

# Breakdown of the expressions based on groups
# 1. g1 = (b*c)
# 2. g2 = (a + g1 / e)
# 3. ans = (g3 / d)

print(ans)

I hope this has helped you understand the groups in expressions. You also must have understood that group operators have the highest precedence in expressions. You must use the parenthesis () to group expressions whenever you wish to enforce a specific order of expression evaluation. It's time for precedence rules.

Precedence and Associativity of Operators

Every operator has a different precedence. Therefore, it's essential to understand the order of evaluation to avoid ambiguity and obtain correct results. Below is the precedence order:

1. Parentheses ()
2. Exponentiation or power **
3. Multiplication *, division /, and modulus %
4. Addition + and subtraction -
5. Assignment operators =, +=, -=, and so on

Understanding operator precedence and associativity is crucial to avoid unexpected results in complex expressions.

Conclusion

Operators and expressions are the foundation of Python programs. They enable us to perform mathematical calculations, compare values, and make logical decisions. Understanding the precedence and associativity of operators is vital for writing accurate and efficient code. By mastering these concepts, you will gain more control over your Python programs and be better equipped to solve a wide range of problems in the world of programming. Happy coding!