Python Coding challenge - Day 593| What is the output of the following Python Code?

 

Code Explanation:

Line 1: def string_only(f):

Defines a decorator function called string_only.

It accepts a function f as an argument (this will be the function we want to "wrap").

Line 2: Define Inner Function wrap(x)

def wrap(x): return f(x) if isinstance(x, str) else "Invalid"

Defines a new function wrap(x) inside string_only.

This function:

Checks if the input x is a string using isinstance(x, str)

If x is a string → calls f(x)

If not → returns "Invalid"

Line 3: Return the Wrapped Function

return wrap

The string_only function returns the wrap function.

This means any function decorated with @string_only will now use this logic.

Line 4–5: Using the Decorator @string_only

@string_only

def echo(s): return s + s

This applies the string_only decorator to the echo function.

So this is equivalent to:

def echo(s): return s + s

echo = string_only(echo)

Now echo is not the original anymore — it’s the wrap function that does a type check first.

Line 6: Calling the Function with Non-String

print(echo(5))

5 is an int, not a string.

So inside wrap(x):

isinstance(5, str) is False

So it returns "Invalid"

Final Output:

Invalid

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