Learn Python for Data Science (Course I)July 18, 2020 2020-08-26 9:26
Learn Python for Data Science (Course I)
- Welcome to Course I!
- Installing Python and Getting Started
- Data Types and Operations in Python
- Control Flow Tools in Python
- Errors and Exceptions in Python
- Classes and Objects in Python
- Standard Libraries in Python
- Virtual Environments and Packages in Python
- Working with Files in Python
- End of Course
Control Flow Tools in Python
In this chapter, you will learn about various control flow tools used in Python.
Control Flow tools in Python are like the ones used in other programming languages. Control flow statements determine what section of code should run in a program at any time. These statements include conditional statements and loops. Let’s discuss each one of them in detail.
1. If statement
The if statement is a conditional statement responsible for executing programming blocks based on specified conditions.
Example of if, elif and else statement in Python:
# Program to find whether a given integer is positive, negative or zero x = int (input( "Please enter an integer: " )) if x < 0: print ('Negative Number') elif x == 0: print ('Zero') elif x > 0: print ('Positive Number') else: print ('None') # This is optional here
OUTPUT: Please enter an integer: -9 Negative Number
2. For loop statement
The for loop statement is a control flow tool in python used to iterate over the items of any sequence (a list or a string) in the order that they appear in the sequence. The syntax of for loop in Python is slightly different from what you may have used in other programming languages, such as C or C++.
Example of for statement in Python:
# Program that iterates over a given list of numbers # Defining a list of integers list_of_numbers = [10, 15, 20, 25, 30, 35] # for statement for number in list_of_numbers: print (number)
OUTPUT: 10 15 20 25 30 35
Using range() function for loops
The range() function generates an arithmetic progression. This function is used for iterating over a sequence of numbers.
Syntax: range(start, stop, step)
- start is the starting value of the range that is inclusive,
- stop is the ending value of the range that is exclusive, and
- step is the value of step used in the progression (optional).
Example of range() function in Python:
# For statement with range() function for x in range(10, 40, 5): # Starting number is with 10 included, stop value is 39, with a step of 5 print (x)
OUTPUT: 10 15 20 25 30 35
3. While loop statement
The While statement is an iterator used to execute a block of statements until the specified condition is matched. It is one of the mostly used control flow tools in Python.
Example of while statement in Python:
# Declaring a variable x x = 10 while x < 35: # run a loop while x is less than 35 x = x + 5 print(x)
OUTPUT: 15 20 25 30 35
4. Break and Continue statement
The break and continue statements alter the flow of a normal loop. The break statement breaks out of the innermost enclosing for or while loop, whereas, the continue statement continues with the next iteration of the loop. In other words, the continue statement escapes the block of the statement below it and starts with the next iteration of the loop.
Example of break and continue statement in Python:
# Defining a list of elements actions = ["wake", "wash", "eat", "work", "play", "sleep"] for action in actions: if action == "sleep": break # if the action is sleep, this would terminate the loop completely elif action == "play": continue # if the action is play, this would not terminate the loop but continues to next iteration else: print (action)
OUTPUT: wake wash eat work
5. Pass statement
The pass statement is one of those control flow tools in python that does nothing. It can be used when a statement is required syntactically, but the program requires no action.
Example of pass statement in Python:
# Program that shows the use of a pass function x = 5 if x == 5: pass # this does nothing
This is what we have for control flow tools in Python. In the next chapter, we will discuss the different types of errors and exceptions in Python.