# Introduction to Scientific Computation Using Python

by Arun Prasaad Gunasekaran

Video 6 : Relational Operators and If construct

## Table of Contents

## Basic Relational Operators in Python

< |
Less than |
`a < b` |
Returns `True` if a is less than b. Else returns `False` . |

<= |
Less than or Equal to |
`a <= b` |
Returns `True` if a is less than or equal to b. Else returns `False` . |

> |
Greater than |
`a > b` |
Returns `True` if a is greater than b. Else returns `False` . |

>= |
Greater than or equal to |
`a >= b` |
Returns `True` if a is greater than or equal to b. Else returns `False` . |

== |
Equal to |
`a == b` |
Returns `True` if a is equal to b. Else returns `False` . |

!= |
Not Equal to |
`a != b` |
Returns `True` if a is not equal to b. Else returns `False` . |

## Basic Logical Operators in Python

or |
Boolean Or |
`con1 or con2` |
Returns `True` if either `con1` or `con2` is `True` . Else returns `False` . |

and |
Boolean And |
`con1 and con2` |
Returns `True` if both `con1` and `con2` are `True` . Else returns `False` . |

not |
Boolean Not |
`not con1` |
Returns `True` if `con1` is `False` |

## If-else construct

if (condition1):
# statements to execute if the condition1 is true
elif (condition2):
# statements to execute if the condition2 is true
elif (condition3):
# statements to execute if the condition3 is true
...
elif (conditionN):
# statements to execute if the conditionN is true
else:
# statements to execute if all the N conditions fail

### Note

The Tabs here are necessary! The tab indicates that the indended statements are a part of the construct.

Check if the inputs actually make a valid triangle.

'''
Program to calculate the area of a triangle using Heron's formulae
'''
# Get inputs
a = float(input("Enter the side 'a' of the triangle:"))
b = float(input("Enter the side 'b' of the triangle:"))
c = float(input("Enter the side 'c' of the triangle:"))
if (a <= 0.0 or b <= 0.0 or c <= 0.0):
print("Sides of a triangle can't be zero or negative!")
elif ( c >= a+b or b >= a+c or a >= b+c):
print("The values violate triangle inequality!")
else:
print("All conditions are valid!")
# Calculate the semi-perimeter
s = (a + b + c)*0.5
# Find the Area
Area = (s*(s-a)*(s-b)*(s-c))**0.5
# Print the result
print("The area of the triangle with sides a = {}, b = {}, and c = {} is {}".format(a, b, c, Area))