Interview Q&A / Python
Python interview questions
Lists, dictionaries, generators, decorators and the Python questions asked in service-company and data roles.
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- What is a decorator in Python and how do you write one?
A decorator is a function that takes another function, wraps it with extra behaviour, and returns the wrapped version. Writing @my_decorator above a function is shorthand for func = my_decorator(func). They are used for logging, timing, caching and access checks without changing the original function's code.
IntermediateIn-depth3 min read - What do the / and * markers in a Python function signature mean?
Parameters before / are positional-only, so callers cannot pass them by name. Parameters after a bare * are keyword-only, so callers must pass them by name. Both make an API clearer and safer to change.
IntermediateQuick answer1 min read - What is a closure in Python?
A closure is an inner function that remembers variables from the enclosing function even after that outer function has finished. It is how Python implements function factories and decorators with private state.
IntermediateQuick answer1 min read - What is the difference between the global and nonlocal keywords in Python?
global makes a name inside a function refer to the module-level variable. nonlocal makes it refer to a variable in the nearest enclosing function. Both are needed only when you assign to the name, not when you just read it.
IntermediateQuick answer1 min read