Conditional Statements and Flow control

Overview

Time: 0 min

Objectives

Understand Conditional Statements and Control Flow statements

Indentation

Unlike other programming languages that use brackets to indicate blocks of code, in python we use indentation.

for i in range(0,5):
  print(i**2)
  print(i)
  print('In for loop')
  print("block")

Python will raise an error if you skip indentation. The number of spaces for each block is up to the programmer. However, it should be atleast one space and the number of spaces should be consistent through out that bloack of code.

Conditional Statements

Conditional statements provide us the ability to test a variable against a value and act in one way if the condition is met by the variable or another way if not.

If Statement

The IF statement is a decision-making statement that guides a program to make decisions based on specified criteria. The IF statement executes one set of code if a specified condition is met (TRUE) or another set of code evaluates to FALSE.

pantry= ['flour',' baking powder','salt','white sugar','milk','egg','butter']

if 'baking powder' in pantry:
  print('We have everything needed to make pancakes!')
else:
  print("You can eat toast!")

if 'syrup' in pantry:
  print('Syrup is optional')
print('Done')

Elif Statement

The elif statement allows you to check multiple expressions for TRUE and execute a block of code as soon as one of the conditions evaluates to TRUE

pantry= ['flour',' baking powder','salt','white sugar','milk','egg','butter']


if 'milk' in pantry:
  print('We have milk')
elif 'non-dairy milk' in pantry:
  print('Non-Dairy milk is available. We can make vegan pancakes if we have Apple Cider vinegar and vanilla instead of eggs and butter')
else:
  print("Incomplete ingredients")

Control Flow

Control Flow is the order in which instructions and function calls are implemented. Thw while and for loop provide us a way to manipulate control Flow

While Loop

The while loop is used to execute a set of statements as long as a condition is true.

butter_in_pantry = 12
servings=0
while butter_in_pantry > 0:
  servings=servings+8
  butter_in_pantry=butter_in_pantry-3
print("Servings:" + str(servings))

We use the BREAK and CONTINUE statements to control the flow of the loop

Break is used to exit the loop
butter_in_pantry = 150
servings=0
while butter_in_pantry > 0:
  servings=servings+8
  if servings >= 24:
    break
  butter_in_pantry=butter_in_pantry-3
Continue is used to stop the current iteration, and continue with the next
label_index = 0
while label_index <= 10:
  label_index += 1
  if label_index == 3:
    continue
  print("Label "+str(label_index))

For Loop

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).

pantry= ['flour',' baking powder','salt','white sugar','milk','egg','butter','cheese','yeast','vanilla extract','oregano','maple syrup','strawberry jam']
for x in ingredients:
  print(x)
  print(" ")

The for loop also has break and continue operators like the while loop

Key Points

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