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🎉 ¡Felicidades! 🎉
¡Has resuelto la tarea brillantemente! Era un reto difícil, pero encontraste la solución correcta. ¡Estás un paso más cerca de dominar la programación! Sigue así, cada etapa superada te hace más fuerte.
Lección 2. Conditions
Dificultad:
Tarea«Viaje en coche»
💻 Python
Alexey es un ávido viajero en automóvil. Planea su próximo gran viaje y quiere asegurarse de poder llegar a la primera ciudad grande sin detenerse a repostar.
rnAntes del viaje, necesita saber si hay suficiente gasolina en el tanque. Ayuda a Alexei y escribe un programa para él.
rnDatos conocidos:
rnEscribe un programa que solicite al usuario dos valores: la cantidad actual de combustible en el tanque (en litros) y la distancia hasta el destino (en kilómetros). El programa debe analizar estos datos y mostrar uno de dos mensajes: "Hay suficiente combustible, ¡puedes ir!" o "Repostaje..."
Formato de entrada
Primera línea: el nivel actual de combustible en el tanque (número real, litros).
Segunda línea: distancia al destino, kilómetros).
Formato de salida
Un mensaje sobre la suficiencia de combustible (línea).
Ejemplo
Entrada
50.0
400.0
Salida
¡Hay suficiente combustible, puedes ir!
Pista
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
Prueba 1
Prueba 2
Prueba 3
Prueba 4
Prueba 5
Prueba 6
Prueba 7
Prueba 8
Prueba 9
Prueba 10
Solución del desarrollador
# Получаем от пользователя текущее количество топлива в литрах и преобразуем в число
current_fuel = float(input())
# Получаем от пользователя расстояние до цели в километрах и преобразуем в число
distance = float(input())
# Рассчитываем, сколько литров топлива потребуется на всю дистанцию
# Расход 10л/100км - это то же самое, что расстояние / 10
fuel_needed = distance / 10
# Проверяем условие: хватит ли топлива с учетом запаса в 5 литров.
# То есть, текущее топливо должно быть больше или равно сумме необходимого на поездку и запаса.
if current_fuel >= fuel_needed + 5:
# Если топлива достаточно, выводим соответствующее сообщение
print("Топлива хватит, можно ехать!")
else:
# Если топлива недостаточно, выводим другое сообщение
print("Нужна дозаправка.")
