Python Python Programming Syllabus

What are the defining properties of a Python set?

A set is an unordered collection of unique (no duplicates) hashable elements. It supports mathematical operations like union (|), intersection (&), and difference (-).

Are Python strings mutable or immutable, and what does indexing 'Python'[0] return?

Strings are immutable. 'Python'[0] returns 'P' (indexing starts at 0).

What is slicing, and what does the slice s[1:4] return for s = 'Python'?

Slicing extracts a substring/subsequence using s[start:stop:step], where stop is exclusive. s[1:4] returns 'yth'.

How does variable assignment work in Python — are variables typed?

Variables are created by assignment (e.g., x = 5) and are untyped references (names) bound to objects. The same variable can be reassigned to a value of any type at any time.

How do you assign multiple variables at once and swap two values in Python?

Multiple assignment: a, b, c = 1, 2, 3. Swap: a, b = b, a.

What is the difference between == and is in Python?

== tests value equality (do the objects have the same value). is tests identity (do two names refer to the exact same object in memory).

What is the basic syntax of an if/elif/else statement in Python?

if condition:\n block\nelif other_condition:\n block\nelse:\n block\nEach branch's body is indented; conditions evaluate to truthy/falsy values.

What is the ternary (conditional) expression syntax in Python?

value_if_true if condition else value_if_false. Example: status = 'pass' if score >= 50 else 'fail'.

Name the three logical operators in Python and what they do.

and (True if both operands true), or (True if at least one true), and not (negates a boolean). and/or use short-circuit evaluation.

What are the two main loop types in Python and when is each used?

The for loop iterates over a sequence/iterable. The while loop repeats as long as a condition remains True.

What does range(2, 10, 2) produce when iterated?

The values 2, 4, 6, 8 (start=2 inclusive, stop=10 exclusive, step=2).

What do the break and continue statements do inside a loop?

break exits the loop immediately. continue skips the rest of the current iteration and proceeds to the next iteration.

What is the purpose of an else clause attached to a Python loop?

The loop's else block runs only if the loop completes normally without hitting a break statement.

What is enumerate() used for in a for loop?

enumerate(iterable) yields pairs of (index, item), letting you access both the position and value: for i, item in enumerate(my_list).

How do you define a function in Python, and what keyword returns a value?

Use the def keyword: def my_func(params):. The return keyword sends a value back to the caller (a function with no return returns None).

What is the difference between positional arguments and keyword arguments?

Positional arguments are matched by their order/position. Keyword arguments are passed by name (e.g., func(x=5)), so order does not matter.

How do you give a function parameter a default value, and what is a caveat?

def f(x, y=10): assigns 10 as the default for y. Caveat: mutable default arguments (like []) are created once and shared across calls; use None as the default instead.

What do *args and **kwargs mean in a function definition?

*args collects extra positional arguments into a tuple. **kwargs collects extra keyword arguments into a dictionary, allowing variable numbers of arguments.

What is a lambda function in Python?

A lambda is a small anonymous function defined inline: lambda args: expression. Example: square = lambda x: x ** 2.

What is a Python docstring and how do you access it?

A docstring is a string literal as the first statement in a function, class, or module, used for documentation. Access it via the object's __doc__ attribute or help(object).

Explain variable scope in Python and the LEGB rule.

LEGB defines name lookup order: Local, Enclosing (nested function), Global (module), Built-in. Python searches these scopes in that order to resolve a name.

What do the global and nonlocal keywords do?

global lets a function rebind a module-level variable. nonlocal lets a nested function rebind a variable in the nearest enclosing (non-global) function scope.

What is a decorator in Python?

A decorator is a function that takes another function and extends/modifies its behavior without changing its code, applied with @decorator_name syntax above a function definition.

What is the Python Standard Library?

A large collection of modules and packages bundled with Python (e.g., math, os, sys, random, datetime, json) providing common functionality without separate installation ('batteries included').

Which standard library module provides mathematical functions, and what does math.sqrt(16) return?

The math module. math.sqrt(16) returns $4.0$ (a float).

What is a Python module, and how do you create one?

A module is a single .py file containing Python definitions and statements. You create one simply by saving code in a file (e.g., mymodule.py) and importing it with import mymodule.

What are three ways to import from a module?

1) import module (then module.name). 2) from module import name (direct access to name). 3) import module as alias (e.g., import numpy as np).

What is the purpose of the if __name__ == '__main__': block?

It contains code that runs only when the file is executed directly as a script, not when it is imported as a module (because __name__ equals '__main__' only for the directly-run file).

What is a Python package, and what file traditionally marks a directory as one?

A package is a directory containing multiple modules, organizing them into a namespace hierarchy. An __init__.py file traditionally marks a directory as a package.

What is the standard built-in function to open a file, and what is the recommended way to ensure it closes?

open(filename, mode) opens a file. Use a with statement (context manager): with open('f.txt') as file: — it automatically closes the file even if an error occurs.

What file modes are used for reading, writing (overwrite), and appending?

'r' = read (default), 'w' = write (creates/truncates/overwrites), 'a' = append (adds to end). Add 'b' for binary (e.g., 'rb') and '+' for read-and-write.

What is the difference between file.read(), file.readline(), and file.readlines()?

read() returns the entire file as one string; readline() returns the next single line; readlines() returns a list of all lines.

How do you write text to a file, and does write() add a newline automatically?

Use file.write(text) (or file.writelines(list)). write() does NOT add a newline automatically — you must include \n yourself.

Why is the os.path / pathlib approach preferred over hardcoding file paths with slashes?

They build OS-independent paths. os.path.join() and pathlib.Path use the correct separator for each operating system (/ on Unix, \\ on Windows), avoiding cross-platform bugs.

What modern module/class provides object-oriented file path handling, and how do you join paths with it?

The pathlib module's Path class. Join paths with the / operator: Path('folder') / 'file.txt'.

What is an exception in Python?

An exception is an error detected during execution that disrupts the normal flow of the program. If unhandled, it propagates up and terminates the program with a traceback.

What is the difference between a syntax error and an exception?

A syntax error occurs at parse time before the program runs (invalid code structure). An exception occurs at runtime during execution of otherwise syntactically valid code.

Name common built-in exceptions for: wrong type, bad value, missing dict key, and division by zero.

TypeError (wrong type), ValueError (right type but invalid value), KeyError (missing dictionary key), and ZeroDivisionError (dividing by zero).

What is the basic try/except syntax for handling an exception?

try:\n risky_code()\nexcept SomeError as e:\n handle(e)\nThe except block runs only if a matching exception is raised in the try block.

What is the purpose of the else and finally clauses in a try statement?

else runs only if the try block raised no exception. finally always runs (whether or not an exception occurred), typically for cleanup like closing resources.

How do you manually trigger an exception in Python?

Use the raise statement, e.g., raise ValueError('invalid input'). You can raise built-in or custom exceptions.

How do you create a custom exception class in Python?

Define a class that inherits from Exception (or a subclass): class MyError(Exception): pass. Then raise it with raise MyError('message').

How can you catch multiple different exception types in Python?

Use multiple except blocks, or group types in a tuple: except (TypeError, ValueError) as e:. Order matters — more specific exceptions should come before general ones.