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Leçon 2. Conditions
Difficulté :
Exercice«Tri de trésors»
💻 Python
Le vieux pirate John Silver est tombé sur un coffre abandonné, dans lequel reposaient trois trésors étranges : un vieux compas, une carte de pirate et un gland en or. Le pirate veut les placer sur une étagère dans sa cabine par ordre de valeur & mdash; du moins cher au plus cher. Mais il est mauvais en mathématiques et vous demande de l'aide.
rnÉcrivez un programme qui prend trois entiers en entrée & mdash; le coût des trois trésors. Le programme doit déterminer leur ordre croissant et afficher les coûts triés à l'écran.
Format d entrée
Trois coûts de trésors (entiers). Chaque nombre est saisi depuis une nouvelle ligne.
Format de sortie
coûts triés des trésors (entiers). Les nombres sont affichés sur une seule ligne, séparés par un espace, dans l'ordre croissant.
Exemple
Entrée
150
25
70
Sortie
25 70 150
Indice
Nested conditions
You can nest some conditional statements (if) into others to create more complex and multi-level checks. This is useful when the next action depends on several consecutive conditions.
The key point here is the correct indentation (usually 4 spaces), which shows Python which block of code belongs to which condition.
Example:
x = 10
if x > 5:
print("First check passed: x is greater than 5.")
if x < 20:
print("Second check passed: x is also less than 20.")
else:
print("Second check failed: x is at least 20.")
else:
print("First check failed: x is less than or equal to 5.")
A useful tip: Try not to create too many nesting levels (3 or more). Deeply embedded code becomes difficult to read and understand. Often, complex nesting can be simplified by using logical operators.
Logical operators
Logical operators in Python are used to combine two or more conditions. They allow you to build complex logic without putting conditions into each other. The main logical operators are and, or and not.
| The | Name | Description |
|---|---|---|
or |
logical "OR" | Returns True if at least one condition is true. |
and |
logical "And" | Returns True only if both conditions are true. |
not |
logical "NOT" (negation) | Inverts the result: True becomes False and vice versa. |
Examples:
a = 5
b = 7
# and: both conditions must be true
s1 = a > 3 and b < 10 # True and True -> True
# or: at least one condition must be true
s2 = a != 5 or b >= 7 # False or True -> True
# not: inverts the result
s3 = not (a < b) # not (True) -> False
When using and, the result will be true only if both operands are true. When using or, it is sufficient for at least one of the operands to be true. The not operator turns a lie into the truth and vice versa.
Analysis of a complex example:
a, b, c = 7, 10, 11
# Original expression:
print(not(a > 7 and b <= 10) or c != 17)
# Let's take it step by step:
# 1. a > 7 -> 7 > 7 -> False
# 2. b <= 10 -> 10 <= 10 -> True
# 3. (False and True) -> False
# 4. not(False) -> True
# 5. c != 17 -> 11 != 17 -> True
# 6. True or True -> True
# Result: True
A useful tip: To improve readability and avoid errors in complex expressions, always use parentheses () to explicitly specify the order of calculations, even if you remember the precedence of operators (not has the highest priority, then and, then or).
The ternary operator
The ternary operator is a compact way to write a simple if-else condition that returns a value. It allows you to assign a variable a value depending on the condition, and all this in one line.
Syntax: [value if true] if [condition] else [value if false]
Examples:
x = 10
# If x > 5, result will be 100, otherwise 200
result = 100 if x > 5 else 200
print(result) # Will output: 100
y = 20
# Assign the larger of the two values to the variable z
z = x if x > y else y
print(z) # Outputs: 20
# Assign a text value
result_text = "positive" if x > 0 else "non-positive"
print(result_text) # Outputs: positive
A useful tip: The ternary operator is great for simple assignments. However, if the logic becomes more complicated or if, depending on the condition, you need to perform different actions (rather than just return a value), it is better to use a full-fledged if-else construct to preserve the readability of the code.
One-line conditions
If the condition body (if, elif, or else) consists of only one instruction, Python allows you to write it in the same line after the colon.
Example:
x = 10
if x > 5: print("x is greater than 5")
Important style note: Although this notation is syntactically correct, it is often not recommended by the Python Code Style Guide (PEP 8). Placing instructions on a separate line with indentation improves readability and is a generally accepted standard. Use a one-line entry with care, mostly for very simple and obvious actions.
main.py
Test 1
Test 2
Test 3
Test 4
Test 5
Test 6
Test 7
Test 8
Test 9
Test 10
Solution du développeur
# Получаем стоимость первого сокровища от пользователя и преобразуем в целое число
treasure1 = int(input())
# Получаем стоимость второго сокровища от пользователя и преобразуем в целое число
treasure2 = int(input())
# Получаем стоимость третьего сокровища от пользователя и преобразуем в целое число
treasure3 = int(input())
# Основной блок условий для определения наименьшего из трёх чисел
# Проверяем, является ли первое сокровище самым дешёвым (или одним из самых дешёвых)
if treasure1 <= treasure2 and treasure1 <= treasure3:
# Если первое сокровище самое дешёвое, сравниваем оставшиеся два
if treasure2 <= treasure3:
# Если второе дешевле третьего, выводим в порядке 1, 2, 3
print(treasure1, treasure2, treasure3)
else:
# Иначе второе дороже третьего, выводим в порядке 1, 3, 2
print(treasure1, treasure3, treasure2)
# Если первое сокровище не самое дешёвое, проверяем, может быть, второе самое дешёвое
elif treasure2 <= treasure1 and treasure2 <= treasure3:
# Если второе сокровище самое дешёвое, сравниваем оставшиеся (первое и третье)
if treasure1 <= treasure3:
# Если первое дешевле третьего, выводим в порядке 2, 1, 3
print(treasure2, treasure1, treasure3)
else:
# Иначе первое дороже третьего, выводим в порядке 2, 3, 1
print(treasure2, treasure3, treasure1)
# Если ни первое, ни второе сокровища не являются самыми дешёвыми, значит, самое дешёвое - третье
else:
# Если третье сокровище самое дешёвое, сравниваем оставшиеся (первое и второе)
if treasure1 <= treasure2:
# Если первое дешевле второго, выводим в порядке 3, 1, 2
print(treasure3, treasure1, treasure2)
else:
# Иначе первое дороже второго, выводим в порядке 3, 2, 1
print(treasure3, treasure2, treasure1)
