# une réponse aux différents premiers exercices des slides

# slide 8/15 :
# swap solution classique :

a = 12
b = 5
if a > b:
    c = a
    a = b
    b = c

# swap solution plus pythonique :
a = 'b'
b = 'A'
if a > b:
    a, b = b, a


# slide 9/15 :
# vérifier si un nombre est premier

import math
v = 154
if v < 2:
    is_prime = False
else:
    is_prime = True
    #max_div = v
    max_div = math.ceil(math.sqrt(v))
    for i in range(2,max_div):
        if v%i == 0:
            is_prime = False
            break

msg = f"number {v} is prime: {is_prime}"
print( msg )


# slides 10:
# Test passage par copie/référence

def test1(a):
    """ return 3.14"""
    print(f"in test1: input value is '{a}'")
    a = 3.14
    return a

def test2(a):
    """ append 3.14 to the input list"""
    a.append(3.14)

v = 12
print(f"v has value '{v}' before call to test1")
v2 = test1(v)
print(f"v has value '{v}' after call to test1")
print(f"return value of test1 call is '{v2}'")

l = [1,'toto', 1.4]
print(f"l has value '{l}' before call to test2")
test2(l)
print(f"l has value '{l}' after call to test2")
res = test2(l)
print(f"the return value of call to test2 is '{res}'")

# Test portée des variables
# global variable definition:
A = 'glob'
def local_var():
    # local variable definition:
    A = 'loc'
    B = 3*A
    print(f"A in local var is '{A}'")
    return B


print(f"A outside call is '{A}'")
res = local_var()
print(f"A after local_var call is '{A}'")

def global_var_read():
    B = 3*A
    print(f"in global_var_read, A is '{A}'")
    return B

res = global_var_read()
print(f"A after global_var_read call is '{A}'")


def global_var_write():
    global A
    A = 'no longer glob '
    print(f"in global_var_write, A is '{A}'")
    return 3*A

res = global_var_write()
print(f"A after global_var_write call is '{A}'")


def global_error():
    # use A from global space, but no global keyword
    B = 3*A
    # thus trying to redefine a local variable with same name
    # will generate an Unbound Local Error
    A = 'loc'
    return B

#global_error()

# swap comme une fonction:
def swap(a,b):
    if a>b:
        return b, a
    else:
        return a, b