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 the difference between a class attribute and an instance attribute, and what does this code print?
A class attribute is shared by all instances. An instance attribute belongs to one object. Assigning through an instance, like a.count = 5, creates a new instance attribute that shadows the class one, but mutating a shared list changes it for everyone.
IntermediateQuick answer1 min read - Why does the second loop over a generator print nothing?
A generator is an iterator, so it can be consumed only once. After the first loop reaches the end, it is exhausted, and later loops or list() calls get no items. Create a new generator, or store the values in a list, to reuse them.
IntermediateQuick answer1 min read - Why does this code raise UnboundLocalError even though x is defined globally?
Assigning to x anywhere inside a function makes x local to the whole function. Reading it before the assignment then fails with UnboundLocalError. Declare global x, or pass x in as an argument, to fix it.
IntermediateQuick answer1 min read