## Week 3: Python Programming Assignment 3 - Problem Analysis and Solutions

This document provides detailed analysis and solutions for each question in Week 3, Assignment 3 of the "Joy of Computing using Python" course on SWAYAM. The assignment tests your understanding of Python's list operations, loops, functions, and conditional logic. Each question is followed by the correct answer and a clear explanation of the reasoning behind it.

**Question 1:**

**Which of the following is/are true statements?**

- A)
**Lists are used to store multiple values.** - B)
**One can access elements in a list by using non-numeric indices.** - C)
**Iterating over lists is possible in Python.** - D)
**We need to specify the required size of a list while creating a new list variable.**

**Correct Answer:** **A) Lists are used to store multiple values.****C) Iterating over lists is possible in Python.**

**Explanation:**

**Option A**is correct because lists in Python can hold multiple elements of any data type.**Option B**is incorrect; list elements in Python can only be accessed using numeric indices.**Option C**is correct; Python allows iteration over lists using loops.**Option D**is incorrect; Python lists are dynamic and do not require a predefined size.

**Question 2:**

**In the below code:**

`python````
n=2
a = []
for i in range(n):
l1 = []
p = 0
for j in range(i):
l1.append(j)
for k in l1:
a.append(p)
p+=1
k=0
for i in a:
k+=1
print(k)
```

**For what value of n does the program print 21?**

**Correct Answer:** **n = 7**

**Explanation:**

To get the output `k = 21`

, you need to determine the sum of the elements appended to list `a`

. As `n`

increases, the value of `k`

(which counts the elements) must match 21, which happens when `n = 7`

.

**Question 3:**

**From the previous question, for what values of n is the number 7 appended to list a?**

- A)
**3** - B)
**6** - C)
**9** - D)
**8**

**Correct Answer:** **B) 6****D) 8**

**Explanation:**

The number `7`

is appended to the list `a`

for specific values of `n`

where the loop structure adds `7`

to the list, which occurs when `n = 6`

and `n = 8`

.

**Question 4:**

**What does the following code perform?**

`python````
def mystery(container):
result = []
for i in range(len(container)):
if i % 2 == 0:
result.append(container[i] * 2)
else:
result.append(container[i] + 3)
return result
```

- A)
**It converts any input list into a new list which is filled with some alternative even and odd numbers.** - B)
**It converts any input list into a new list such that at even indices, the value is a multiple of an even number and at odd indices, the value is either odd or even number.** - C)
**It converts any input list into a new list such that at even indices, the value is a multiple of 2 and at odd indices, the value is a multiple of 3.** - D)
**It converts any input list into a new list, which follows no pattern.**

**Correct Answer:** **C) It converts any input list into a new list such that at even indices, the value is a multiple of 2 and at odd indices, the value is a multiple of 3.**

**Explanation:**

The code multiplies elements at even indices by 2 and adds 3 to elements at odd indices, resulting in a list where values at even indices are multiples of 2 and those at odd indices are multiples of 3.

**Question 5:**

**From the previous question, if the option in question 4 is incorrect, can you make changes to the code such that this option is true?**

**Correct Answer:** **Yes, we can make changes.**

**Explanation:**

Modifications to the function can ensure that the list generated aligns with the expected pattern of even and odd numbers.

**Question 6:**

**If the file exists, does the code successfully run?**

`python````
with open("file.txt", "w") as f:
data = f.read()
print(data)
```

- A)
**Yes** - B)
**No**

**Correct Answer:** **B) No**

**Explanation:**

The code will not run successfully because the file is opened in write mode `"w"`

, which erases the content of the file if it exists and does not allow reading. The correct mode to read from the file should be `"r"`

or `"r+"`

.

**Question 7:**

**Which of the following are examples of Social Computing?**

- A)
**StackOverflow** - B)
**Wikipedia** - C)
**Quora** - D)
**None**

**Correct Answer:** **A) StackOverflow****B) Wikipedia****C) Quora**

**Explanation:**

All three platforms—StackOverflow, Wikipedia, and Quora—are examples of Social Computing, as they enable collaborative and social interaction among users, sharing knowledge and content.

**Question 8:**

**What does the following code print for n = 3?**

`python````
n=3
a = []
k = 0
while k * (k + 1) < 10:
k += 1
a.append(k * (k + 1))
a.sort()
for i in a:
if i > n * n:
print("WE KNOW THE WISDOM OF SERIES")
break
else:
print("WE ARE YET TO KNOW MANY THINGS")
```

- A)
**WE KNOW THE WISDOM OF SERIES** - B)
**WE ARE YET TO KNOW MANY THINGS**

**Correct Answer:** **B) WE ARE YET TO KNOW MANY THINGS**

**Explanation:**

For `n = 3`

, the maximum value of `i`

in the list `a`

does not exceed `n*n = 9`

, so the code does not enter the `if`

statement, and the `else`

clause executes.

**Question 9:**

**From the previous question, is the variable a or a.sort() responsible for printing either of the two possible sentences?**

- A)
**No, it is not dependent on variable**`a`

, the code will never print "WE ARE YET TO KNOW MANY THINGS". - B)
**Yes, on**`a.sort()`

only, but the code will never print "WE ARE YET TO KNOW MANY THINGS". - C)
**Yes, on both, the code may print both sentences.** - D)
**No, it is dependent on**`a.sort()`

, the code will never print "WE ARE YET TO KNOW MANY THINGS".

**Correct Answer:** **C) Yes, on both, the code may print both sentences.**

**Explanation:**

The variable `a`

and the `a.sort()`

operation determine the order of elements in `a`

, which affects whether the `if`

condition is met and thus which sentence is printed.

**Question 10:**

**What does the code in question 8 calculate? Can you say what the values of k and n are if n = 1023492674982341 x 129198?**

**Correct Answer:** **If values of k and n are different, enter 0, else enter value of k.**

**Explanation:**

This question prompts you to compute a mathematical operation based on the given `n`

and check if `k`

and `n`

yield the same result after specific operations. The problem needs a detailed mathematical explanation based on the values provided.