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Lektion 2. Conditions
Schwierigkeit:
Aufgabe«Klima im Gewächshaus»
💻 Python
Du & mdash; Agron, verantwortlich für das moderne automatisierte Gewächshaus. Deine Aufgabe & mdash; Schreibe ein Programm für einen Mikrocontroller, der das Klima steuert. Das System soll Daten von Temperatur- und Feuchtigkeitssensoren analysieren und einen von drei Befehlen ausgeben: „Heizung einschalten“, „Pflanzen gießen“ oder melden, dass „alles in Ordnung ist“.
rnDie Bedingungen:
rn- rn
- Die Kälteprüfung hat die höchste Priorität. Wenn die Temperatur & nbsp; unter 15 & nbsp; Grad fällt, muss dringend die Heizung eingeschaltet werden, unabhängig von der Luftfeuchtigkeit. rn
- Wenn es im Gewächshaus nicht kalt ist, muss geprüft werden, ob gegossen werden muss. Gießen ist erforderlich, wenn die Temperatur & nbsp; über 25 & nbsp; Grad oder die Luftfeuchtigkeit & nbsp; unter 50% liegt. rn
- Wenn keine der obigen Bedingungen erfüllt ist, ist das Klima im Gewächshaus optimal. rn
Das Programm erhält zwei ganze Zahlen (Temperatur und Luftfeuchtigkeit) und gibt den entsprechenden Befehl auf dem Bildschirm aus.
Eingabeformat
Zwei ganze Zahlen, jede in einer neuen Zeile. Die erste & mdash; Temperatur (ganze Zahl), die zweite & mdash; Luftfeuchtigkeit (ganze Zahl).
Ausgabeformat
Eine Zeile mit einer Empfehlung (Zeile).
Beispiel
Eingabe
28
60
Ausgabe
Wasserpflanzen
Hinweis
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
Entwicklerlösung
# Считываем показания датчиков с двух разных строк
temperature = int(input()) # Вводим температуру и преобразуем в целое число
humidity = int(input()) # Вводим влажность и преобразуем в целое число
# Проверяем условия по заданному приоритету
if temperature < 15:
# Сначала проверяем на холод, так как это самый критичный параметр
print("Включить отопление")
elif temperature > 25 or humidity < 50:
# Если не холодно, проверяем, не жарко ли или не сухо ли
print("Поливать растения")
else:
# Если все предыдущие проверки не сработали, значит, условия оптимальны
print("Всё в порядке")
