THEORY AND PRACTICE

Input and Output Data

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Conditions

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Занятие 2. Conditions

Difficulty level:

Task«The wizard spell»

the young wizard Alex found a recipe for levitation spell in ancient make-up. The book says that three key components are needed for success: a tears of griffin, Mandrahore root and moon dust. The old wizard-mentor told Alex that the spell would work only if at least two of the three ingredients will be added correctly.

Write the program to verify whether his gluing will work. The program should request the condition of each of the three ingredients. The user introduces & nbsp; 1 , if the ingredient is added correctly (truth), and & nbsp; 0 , if wrong (lies). 14pt; "> Depending on the entered data, the program should display one of two results:" The spell worked! " or "The spell did not work.".

Input format

the condition of the first ingredient (integer: 1 or 0)
the state of the second ingredient (integer: 1 or 0)
the state of the third ingredient (integer: 1 or 0)

Output format

The result of the spell (line)

Example

Input

1
1
0

Output

The spell worked!

Hint

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

Developer’s solution

# Запрашиваем у пользователя состояние для каждого из трёх ингредиентов.
# Используем int() для преобразования введённой строки в целое число (0 или 1).
ingredient1 = int(input())
ingredient2 = int(input())
ingredient3 = int(input())

# Складываем значения всех трёх переменных.
# Если два или три ингредиента верны (1), сумма будет 2 или 3.
# Если верных ингредиентов меньше двух, сумма будет 0 или 1.
correct_ingredients_count = ingredient1 + ingredient2 + ingredient3

# Проверяем условие: если количество верных ингредиентов больше или равно двум.
if correct_ingredients_count >= 2:
    # Если условие истинно, выводим сообщение об успехе.
    print("Заклинание сработало!")
else:
    # Если условие ложно, выводим сообщение о неудаче.
    print("Заклинание не сработало.")

🎉 Congratulations! 🎉

You did an excellent job with the task! It was a challenging problem, but you found the correct solution. You are one step closer to mastering programming! Keep up the good work, because every stage you pass makes you even stronger.