Python Basics & Programming Fundamentals: Class XI & XII Practice Worksheets (With Answers)

COMPUTER SCIENCE / INFORMATICS PRACTICES

Worksheet Set 1: Introduction, Features & Execution Modes

Answer Key – Set 1

Ans 1: Python is a high-level, interpreted, general-purpose programming language developed by Guido van Rossum and released in 1991.

Ans 2: (i) Easy to read and learn, (ii) Interpreted language, (iii) Platform-independent / Dynamically typed.

Ans 3:

print("Hello World")

Ans 4: Interactive mode allows typing commands directly next to the primary prompt (`>>>`) for immediate execution line-by-line. Script mode involves writing a sequence of statements in a file and saving it before running the entire file at once.

Ans 5: Three greater-than signs (>>>).

Ans 6: .py

Ans 7: Yes, Python is case-sensitive. Age and age are treated as two entirely distinct identifiers/variables because uppercase and lowercase letters have different ASCII values.

Ans 8: Python is interpreted because its code is executed line-by-line by an interpreter program rather than being compiled entirely into machine code beforehand.

Ans 9: Yes, using the command line tool: python filename.py.

Ans 10: No manual compilation is required by the programmer; the Python interpreter automatically compiles source code into intermediate bytecode behind the scenes before execution.

COMPUTER SCIENCE / INFORMATICS PRACTICES

Worksheet Set 2: Python Character Set & Tokens

Answer Key – Set 2

Ans 1: A token is the smallest individual unit in a Python program. Types: Keywords, Identifiers, Literals, Operators, Punctuators.

Ans 2: Keywords are reserved words with predefined meanings for the Python interpreter. No, they cannot be used as variable names because doing so would redefine the language’s core syntax rules.

Ans 3: An identifier is a user-defined name given to variables, functions, classes, etc. Rules: (i) Must begin with a letter or underscore, (ii) Cannot contain special characters except underscore.

Ans 4: Valid: _total, emp_salary. Invalid: 1st_var (starts with a digit), for (is a keyword), my-var (contains hyphen).

Ans 5: Literals are data items that have fixed/constant values. Types: Numeric literals, String literals, Boolean literals, Special literal (None).

Ans 6: Arithmetic: +, %. Relational: >=, ==. Logical: and, not.

Ans 7: Punctuators are symbols used in programming to organize sentence structures and indicate the rhythm of code. Examples: [], {}, #, ,.

Ans 8: The Python character set is a set of valid characters recognized by Python, including letters (A-Z, a-z), digits (0-9), whitespace, and special symbols.

Ans 9: Integer literals are whole numbers without decimal points (e.g., 45, -3), whereas floating-point literals contain fractional decimal parts (e.g., 45.5, -0.002).

Ans 10: 4 tokens: sum (identifier), = (operator), x (identifier), + (operator), 10 (literal). Total = 5 tokens.

COMPUTER SCIENCE / INFORMATICS PRACTICES

Worksheet Set 3: Variables, l-values, r-values & Comments

Answer Key – Set 3

Ans 1: A variable is a named memory location used to store data values. It is created simply by assigning a value to a name using the assignment operator (=).

Ans 2: An l-value refers to an object that has a memory address (usually a variable name on the left side of an assignment). An r-value refers to a data value or expression evaluated on the right side of an assignment.

Ans 3: score is the l-value, and 95 is the r-value.

Ans 4: No, because l-values must represent writable memory locations (variables). Constants or expressions cannot store values, resulting in a syntax error if placed on the left side.

Ans 5: Comments are readable notes included in code for documentation purposes to help programmers understand code logic.

Ans 6: Single-line comments start with the hash symbol (#). Multi-line comments can be created either by placing consecutive # lines or using triple-quoted strings (''' or """).

Ans 7: No, comment lines are completely ignored by the Python interpreter during execution.

Ans 8: No output will be produced because the statement is commented out with a hash (#).

Ans 9: Python is dynamically typed, meaning the data type of a variable is determined automatically by the interpreter based on the value assigned to it at runtime.

Ans 10: x acts as **both**: on the left side (l-value) it represents the memory location where the new value is stored, and on the right side (r-value) its current value is fetched for addition.