PYTHON > les tests, if, elif, else

GENERALITES

if b > a :
   print("b est plus grand que a")

 

a == b - a != b - a < b - a <= b - a > b - a >= b

if … elif … else

if b > a:
   print("b plus grand que a")
elif a == b:
   print("a et b sont égaux")

 

if b > a:
   print("b is greater than a")
elif a == b:
   print("a and b are equal")
else:
   print("a is greater than b")

FORME COURTE

if a > b: print("a est plus grand que b")

if … else

print("A") if a > b else print("B")
print("A") if a > b else print("=") if a == b else print("B")

 

a = '123' if b else '456'

 

<condition> ? <expression1> : <expression2>

 

expression1 if <condition> else <expression2>

 

D’abord ça évalue la <condition>, si True, <expression1> sera retournée, sinon, ce sera <expression2>

Evaluation is lazy, so only one expression will be executed.

 

age = 15
print('ado' if age < 18 else 'adulte') # les conditions sont évaluées de gauche à droite
ado

 

age = 15
print('kid' if age < 13 else 'teenager' if age < 18 else 'adult')
teenager
age = 15
print(('adult', 'kid')[age < 20]) # Selecting an item from a tuple
kid
print(('adult', 'kid')[True])
kid
print({True: 'kid', False: 'adult'}[age < 20])
kid

The problem of such an approach is that both expressions will be evaluated no matter what the condition is. As a workaround, lambdas can help:

>>> age = 15
>>> print((lambda: 'kid', 'lambda: adult')[age > 20]())
kid

 

age = 15
print(((age < 20) and ['kid'] or ['adult'])[0])
kid

OU - ET

if a > b and c > a:
   print("Both conditions are True")

 

if a > b or a > c:
   print("At least one of the conditions is True")

 

—

 

VOIR : https://www.w3schools.com/python/python_conditions.asp

 

—

 

toto = true
if toto:

EXEMPLES

Tester si nombre est pair

if nombre % 2 == 0:

Tester si un caractère est présent dans un texte

if lettre in 'abcdef':

 

if lettre not in '!@#$%^&*()_+[]{}' and x is not chr(10):

 

—