Python Closures

1) Simple Closure

Write a function outer() that defines a local variable x = 5 and returns an inner function that prints x. Call the closure.

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2) Closure With Parameter

Create outer(a) that returns a function which prints a. Test with different values.

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3) Add Using Closure

Write make_adder(x) that returns a function adding x to its argument. Test with add5 = make_adder(5) → add5(10).

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4) Multiply Using Closure

Write make_multiplier(n) that returns a function to multiply input by n. Test with different multipliers.

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5) Personalized Greeting Closure

Write a function that returns a greeting function based on a given name.

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6) Counter Closure

Create make_counter() that returns a function which increments and returns a count starting at 0 each time it’s called.

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7) Closure With Default

Use a default inner function to add a fixed tax percentage to an amount.

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8) Store Value in Closure

Use a closure to store a secret value and retrieve it via the returned function.

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9) Change Outer Variable

Write a closure that changes an outer variable using nonlocal.

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10) Closure That Formats Text

Write make_formatter(prefix) that returns a function to print text with that prefix.

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11) Closure Returning Boolean

Write a closure that checks if a number is greater than a fixed threshold.

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12) Closure to Filter List

Create make_filter(n) that returns a function filtering numbers greater than n from a list.

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13) Closure to Accumulate Sum

Write make_accumulator() that returns a function accumulating sum across calls.

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14) Closure With Multiple Parameters

Write outer(a,b) that returns an inner function computing a * b plus input.

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15) Replace Built-in Behavior

Use closure to modify the behavior of a function — for example, always convert text to uppercase before printing.

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16) Delay Execution With Closure

Write a function that returns a closure which prints a message only when called later.

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17) Generate Sequence Using Closures

Write create_seq(start) that returns a function generating next number on each call.

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18) Powers Using Closure

Write power_of(n) returning a function that raises input to power n.

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19) Conditional Rate Calculator

Write a closure that applies different rates (e.g., tax/discount) based on flags.

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20) Decorator-like Closure

Create a simple closure that wraps another function to print “Start” and “End” around its execution.

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🧠 Key Concepts Practiced

Concept	Example Focus
Nested functions	Inner fn defined inside outer fn
Returning functions	Outer returns inner
Capturing outer variables	Closure remembers outer state
Using closures for custom behavior	adders, multipliers, filters
nonlocal keyword	Modifying outer variable

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📌 Mini Example

Adder closure

def make_adder(x):
    def adder(y):
        return x + y
    return adder

add5 = make_adder(5)
print(add5(10))  # 15

Counter closure

def make_counter():
    count = 0
    def counter():
        nonlocal count
        count += 1
        return count
    return counter

c = make_counter()
print(c())  # 1
print(c())  # 2

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