Writing multiple lines in Python - Time & Space Complexity

Time Complexity: Writing multiple lines

O(n)

Understanding Time Complexity

When writing multiple lines in a program, it is important to see how the time to run the code changes as we add more lines.

We want to know how the program's work grows when we write many lines one after another.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

for i in range(n):
    print(i)

for j in range(n):
    print(j * 2)
    

This code prints numbers from 0 to n-1, then prints double those numbers in a second loop.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Two separate loops that each run through n items.
• How many times: Each loop runs n times, one after the other.

How Execution Grows With Input

Explain the growth pattern intuitively.

Input Size (n)	Approx. Operations
10	About 20 print actions
100	About 200 print actions
1000	About 2000 print actions

Pattern observation: The total work grows roughly twice as fast as n because there are two loops each doing n steps.

Final Time Complexity

Time Complexity: O(n)

This means the time to run the code grows in a straight line as the input size grows, even with two loops one after another.

Common Mistake

[X] Wrong: "Two loops mean the time complexity is squared, like O(n²)."

[OK] Correct: The loops run one after the other, not inside each other, so the total time just adds up, not multiplies.

Interview Connect

Understanding how multiple steps add up helps you explain your code clearly and shows you know how programs grow with input size.

Self-Check

"What if the two loops were nested inside each other? How would the time complexity change?"

Practice

1. Which of the following is the correct way to write a string that spans multiple lines in Python?

easy

A. Use double quotes but write all text in one line only

B. Use single quotes and separate lines with commas

C. Use triple quotes like '''This is a\nmulti-line string'''

D. Use backslashes at the end of each line without quotes

Solution

1. Step 1: Understand multi-line string syntax

   Python allows strings to span multiple lines using triple quotes (either ''' or """).

2. Step 2: Check each option

   Use triple quotes like '''This is a\nmulti-line string''' correctly uses triple quotes to write a multi-line string. Other options misuse quotes or syntax.

3. Final Answer:

   Use triple quotes like '''This is a\nmulti-line string''' -> Option C

4. Quick Check:

   Triple quotes = multi-line string [OK]

Hint: Remember: triple quotes let strings span multiple lines easily [OK]

Common Mistakes:

• Using single or double quotes without triple quotes
• Trying to separate lines with commas inside quotes
• Forgetting to close triple quotes

2. Which of these code snippets correctly prints multiple lines using a multi-line string?

easy

A. print('''Line 1\nLine 2\nLine 3''')

B. print('Line 1\n' + 'Line 2\n' + 'Line 3')

C. print('Line 1\nLine 2\nLine 3')

D. print('''Line 1
Line 2
Line 3''')

Solution

1. Step 1: Understand how multi-line strings handle newlines

   Triple-quoted strings keep line breaks as typed, so actual newlines appear without \n escape sequences.

2. Step 2: Analyze each option

   print('''Line 1 Line 2 Line 3''') uses triple quotes with actual newlines inside, so it prints three lines. print('''Line 1\nLine 2\nLine 3''') uses \n inside triple quotes, which prints literal \n, not new lines. Options B and D use single quotes with \n, which print new lines correctly, but are not multi-line strings.

3. Final Answer:

   print('''Line 1 Line 2 Line 3''') -> Option D

4. Quick Check:

   Triple quotes with real newlines print multiple lines [OK]

Hint: Triple quotes keep line breaks as typed, no need for \n [OK]

Common Mistakes:

• Using \n inside triple quotes expecting line breaks
• Confusing escape sequences with actual newlines
• Using single quotes for multi-line strings

3. What will be the output of this code?

text = '''Hello
World
Python'''
print(text)

medium

A. Hello
World
Python

B. Hello\nWorld\nPython

C. Hello World Python

D. SyntaxError

Solution

1. Step 1: Understand triple-quoted string behavior

   The triple quotes preserve the line breaks inside the string as actual newlines.

2. Step 2: Predict print output

   Printing the string will show three lines: Hello, World, and Python each on its own line.

3. Final Answer:

   Hello World Python -> Option A

4. Quick Check:

   Triple quotes print multi-line text as typed [OK]

Hint: Triple quotes print text with real line breaks, not \n literals [OK]

Common Mistakes:

• Expecting \n to print literally
• Confusing string representation with print output
• Syntax errors from missing quotes

4. Find the error in this code that tries to print multiple lines:

text = '''Line 1
Line 2
Line 3'
print(text)

medium

A. Missing closing triple quotes causes SyntaxError

B. Using single quotes inside triple quotes is not allowed

C. print() function is missing parentheses

D. No error, code runs fine

Solution

1. Step 1: Check string delimiters

   The string starts with triple single quotes ''' but ends with a single quote ', causing a syntax error.

2. Step 2: Identify error type

   Python expects matching triple quotes to close the string. Mismatched quotes cause SyntaxError.

3. Final Answer:

   Missing closing triple quotes causes SyntaxError -> Option A

4. Quick Check:

   Triple quotes must open and close properly [OK]

Hint: Triple quotes must match exactly at start and end [OK]

Common Mistakes:

• Ending triple-quoted string with single quote
• Forgetting to close triple quotes
• Assuming print syntax error instead

5. You want to store a long message with multiple paragraphs in a variable and print it exactly as typed, including blank lines. Which is the best way to do this?

hard

A. Concatenate many single-line strings with + and \n

B. Use triple quotes to write the message with blank lines inside

C. Use single quotes and write all text in one line with \n

D. Use multiple print statements for each line

Solution

1. Step 1: Understand requirement for preserving formatting

   To keep multiple paragraphs and blank lines exactly as typed, the string must preserve line breaks and spaces.

2. Step 2: Choose best method

   Triple quotes allow writing multi-line strings naturally, including blank lines, without needing \n or concatenation.

3. Final Answer:

   Use triple quotes to write the message with blank lines inside -> Option B

4. Quick Check:

   Triple quotes preserve formatting best for long multi-line text [OK]

Hint: Triple quotes keep all line breaks and spaces as typed [OK]

Common Mistakes:

• Using concatenation makes code messy and error-prone
• Forgetting to add \n for new lines in single quotes
• Using multiple print statements loses single string storage