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2: Python Basics - Variables and Functions#

1. Variables and Operations#

There are 4 main types of variables

  • int (integer)

  • float (decimal number)

  • string (string of characters)

  • bool (boolean)

x = 3 # type int 
y = 2.5 # type float
first_name = 'Amine' # type string
z = True # type Bool

# Arithmetic operations
print('x + y =', x + y)
print('x - y =', x - y)
print('x / y =', x / y)
print('x // y =', x // y) # integer division (very useful for Numpy tables)
print('x * y =', x * y)
print('x ^ y =', x ** y) # x power y

x + y = 5.5
x - y = 0.5
x / y = 1.2
x // y = 1.0
x * y = 7.5
x ^ y = 15.588457268119896

# Comparison operations
print('equality:', x == y)
print('inequality:', x != y)
print('less than or equal to:', x <= y)
print('greater or equal:', x >= y)

equality: False
inequality: True
less than or equal to: False
greater or equal: True

# Opérations Logiques
print('AND :', False and True)
print('OR :', False or True)
print('XOR :', False ^ True)

AND : False
OR : True
XOR : True

Note: Comparison and logic operations used together allow to build basic algorithmic structures (if/esle, while, …)

2. Functions#

An anonymous function is a function created with lambda. This type of function is basic and is useful to be integrated in the middle of control structures or other functions. It is rarely used.

Hide code cell content 
# Exemple of a lambda function f(x) = x^2
f = lambda x : x**2

print(f(3))

9

# Exemple2: g(x, y) = x^2 - y^2
g = lambda x, y : x**2 - y**2

print(g(4, 2))

12

The best way to create a function is to use the following structure: def

# Exemple: a function has a name, takes inputs (arguments) and transforms them to return a result

def function_name(argument_1, argument_2):
    result = argument_1 + argument_2
    return result

function_name(3, 2)

5

# Concrete example : function that calculates the potential energy of a body

def e_potential(mass, height, g=9.81):
    energy = mass * height * g 
    return energy

# here g has a default value so we don't have to give it a value
e_potential(mass=10, height=10)

981.0

3. Exercise and Solution#

Modify the e_potential function defined above to return a value indicating whether the computed energy is greater or less than a limit_energy passed as the 4th argument

Solution :#

Hide code cell content 
def e_potential(mass, height, e_limit, g=9.81):
    energy = mass * height * g 
    return energy > e_limit

e_potential(mass=10, height=10, e_limit=800)

True