Python Interview Questions
Variables, built-in data types, dynamic vs strong typing, and Python's core equality and mutability rules.
Ans
A Python variable is a name bound to an object. Assignment does not declare a fixed variable type; the same name can later refer to an object of another type.
Example
pythonx = 10 x = "Python" print(x)
Important Point
The object has a type; the name is a reference/binding to that object.
Ans
Common built-in types include int, float, complex, bool, str, list, tuple, set, dict, bytes, bytearray, range, and NoneType. Python also lets developers create custom classes.
Example
pythonage = 25 name = "Amit" marks = [80, 90]
Important Point
Use `type()` or `isinstance()` when type inspection is actually needed.
Ans
Dynamic typing means the type associated with a value is determined at runtime and a name can be rebound to objects of different types.
Example
pythonvalue = 10 value = "ten"
Important Point
Dynamic typing does not remove type checking; many type errors are discovered when the relevant code executes.
Ans
Python generally does not perform arbitrary implicit conversions between unrelated types. For example, adding a string and an integer raises TypeError.
Example
python# "10" + 5 # TypeError result = int("10") + 5 print(result)
Important Point
Explicit conversion is clearer and safer when values come from external sources.
Ans
Indentation is part of Python's syntax and defines code blocks instead of braces. Consistent indentation is therefore required.
Example
pythonif age >= 18: print("Adult")
Important Point
Mixing tabs and spaces inconsistently can cause indentation errors; four spaces is the common convention.
Ans
PEP 8 is Python's style guide. It recommends conventions for formatting, naming, imports, whitespace, and code layout to improve readability.
Example
pythondef calculate_total(price, tax): return price + tax
Important Point
PEP 8 is a style guideline, not a rule that changes Python's execution semantics.
Ans
None is Python's singleton value representing the absence of a value or a deliberate 'no result' state.
Example
pythondef find_user(user_id): return None print(find_user(10) is None)
Important Point
Use `is None` rather than `== None` for the usual identity check.
Ans
Mutable objects can be changed after creation, while immutable objects cannot. Lists and dictionaries are mutable; strings, tuples, integers, and frozensets are immutable.
Example
pythonitems = [1, 2] items.append(3) # mutation name = "Py" name += "thon" # creates/rebinds a string
Important Point
A tuple is immutable as a container, but it can contain a mutable object whose state changes.
Ans
Type conversion changes a value from one type to another using constructors or conversion functions such as int(), float(), str(), list(), and tuple().
Example
pythonage = int("25") price = float("19.5") print(age + 1)
Important Point
Conversion can fail, such as `int("abc")`, which raises ValueError.
Ans
== compares values for equality, while is checks whether two references point to the same object. Use == for value comparison and is mainly for identity checks such as None.
Example
pythona = [1, 2] b = [1, 2] print(a == b) # True print(a is b) # False
Important Point
Do not use `is` as a general replacement for `==`.