Python programming is an increasingly important sub-topic of “Basics of Mechatronics” (Section A.2) in the GATE Robotics and Automation (RA) 2027 syllabus. The questions are practical and predictable: trace the output of a snippet, evaluate an operator or expression, follow a loop or conditional, or unwind a recursive function. This guide reviews the core Python constructs on the syllabus and works through six GATE-style output-prediction problems in full.
TABLE OF CONTENTS
Data types & operators
Python’s core types are int, float, str, bool, list, tuple, dict and set. The two operators that trip candidates up are integer division // (floor division) and modulo % (remainder), alongside exponentiation **. Knowing that 17 // 5 = 3 and 17 % 5 = 2 answers a whole class of arithmetic questions.
Conditionals & loops
Control flow uses if / elif / else for branching and for / while for iteration, with break and continue to alter loop flow. The built-in range(a, b) yields a, a+1, …, b−1 — the upper bound is exclusive, which is the single most common source of off-by-one errors.
Functions & recursion
Functions are defined with def and can call themselves (recursion). A recursive function needs a base case and a recursive step: factorial(n) = n × factorial(n−1) with factorial(0) = 1, and the Fibonacci sequence fib(n) = fib(n−1) + fib(n−2). Tracing the call stack gives the answer.
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Strings, lists & dictionaries
Strings and lists support zero-based indexing and slicing s[a:b] (b exclusive), with negative indices counting from the end. List comprehensions build lists concisely, e.g. [x**2 for x in range(5)]. Dictionaries store key–value pairs with O(1) average lookup. These collection operations dominate the coding questions.
Worked examples (GATE-style)
Example 1 — integer division and modulo
What do 17 // 5 and 17 % 5 evaluate to?
Solution. 17 // 5 is the floor of 3.4 = 3; 17 % 5 is the remainder = 2.
Check: 5×3 + 2 = 17. ✓
Example 2 — loop sum
What is the output of s = 0; for i in range(1, 6): s += i; print(s)?
Solution. range(1, 6) gives 1, 2, 3, 4, 5 (6 is excluded). Their sum is 1+2+3+4+5.
Output = 15.
Example 3 — recursion (factorial)
A function is defined as f(n) = 1 if n == 0 else n * f(n-1). What is f(5)?
Solution. This is the factorial: 5 × 4 × 3 × 2 × 1.
f(5) = 120.
Example 4 — string slicing
For s = "robotics", what are s[0:5] and s[-3:]?
Solution. s[0:5] takes indices 0–4 = “robot” (index 5 excluded).
s[-3:] takes the last three characters = “ics”.
Example 5 — list comprehension
What list does [x**2 for x in range(5)] produce?
Solution. x runs over 0, 1, 2, 3, 4; squaring each gives 0, 1, 4, 9, 16.
Output = [0, 1, 4, 9, 16].
Example 6 — recursion (Fibonacci)
With fib(n) = n if n < 2 else fib(n-1) + fib(n-2), what is fib(6)?
Solution. The sequence is fib(0)=0, 1, 1, 2, 3, 5, and fib(6) = fib(5) + fib(4) = 5 + 3.
fib(6) = 8.
Quick reference
QUICK REFERENCE
Floor / mod: 17 // 5 = 3, 17 % 5 = 2
range(a, b): a … b−1 (b excluded)
Slicing: s[a:b] → indices a … b−1
Negative index: s[−1] = last element
Factorial: f(n) = n·f(n−1), f(0) = 1
Comprehension: [x**2 for x in range(5)] = [0,1,4,9,16]
Common mistakes to avoid
- Treating range(a, b) as inclusive — the upper bound b is excluded.
- Confusing / and // — single slash gives a float, double slash floors to an int.
- Off-by-one in slicing — s[a:b] stops at index b−1.
- Missing the recursion base case, which causes infinite recursion.
- Assuming lists and tuples behave the same — tuples are immutable.
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Basics of Mechatronics — full solved-problem series
This guide is one part of the Section A.2 (Basics of Mechatronics) solved-problem series. Work through every sub-topic:
See also the umbrella guide, Basics of Mechatronics — Important Questions, and the complete GATE RA 2027 Syllabus.
Frequently asked questions
What is the difference between / and // in Python?
The single slash / performs true division and always returns a float (7 / 2 = 3.5), while the double slash // performs floor division and returns the largest integer not exceeding the quotient (7 // 2 = 3).
Does range(a, b) include b?
No. range(a, b) generates values from a up to b−1; the upper bound is exclusive. So range(1, 6) yields 1, 2, 3, 4, 5 — five values.
Why does a recursive function need a base case?
The base case stops the recursion. Without it, the function keeps calling itself indefinitely until the interpreter raises a “maximum recursion depth exceeded” error. For factorial, the base case is f(0) = 1.
This solved-problems guide is part of the complete GATE RA 2027 Syllabus overview and the Basics of Mechatronics syllabus guide.
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