String creation and representation in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are the three ways to create a string in Python?

You can create strings using single quotes ('example'), double quotes ("example"), or triple quotes ('''example''' or """example"""). Triple quotes allow multi-line strings.

intermediate

How does Python represent strings internally?

Python stores strings as sequences of Unicode characters, allowing support for many languages and symbols beyond ASCII.

intermediate

What is the difference between raw strings and normal strings in Python?

Raw strings (prefix r or R) treat backslashes (\) as literal characters and do not interpret escape sequences like \n or \t.

beginner

How can you include quotes inside a string without ending it?

You can use different quotes to surround the string than the ones inside it, for example: "He said 'hello'" or 'She said "hi"'. Alternatively, use escape characters like \" or \'.

intermediate

What does the repr() function do with strings?

repr() returns a string representation that shows the string with quotes and escape characters, useful for debugging.

Which of these is a valid way to create a multi-line string in Python?

A Using double quotes " only

B Using single quotes ' only

C Using triple quotes ''' or """

D Using backticks `string`

Triple quotes allow strings to span multiple lines.

What does the prefix r before a string mean in Python?

A It creates a raw string where backslashes are treated literally

B It reverses the string

C It makes the string uppercase

D It removes all spaces

Raw strings do not process escape sequences like \n.

How can you include a double quote inside a string defined with double quotes?

A Use single quotes inside double quotes without escape

B Just type it without any special character

C You cannot include double quotes inside double quotes

D Escape it with a backslash like \"

Escape characters allow including quotes inside strings.

What will repr('Hello\nWorld') return?

A 'Hello\nWorld'

B Hello World

C Hello World

D Error

repr() shows the string with escape characters visible.

Which statement about Python strings is true?

A Strings can only contain ASCII characters

B Strings are sequences of Unicode characters

C Strings are mutable (can be changed)

D Strings must be enclosed in single quotes only

Python strings support Unicode and are immutable.

Explain how to create strings in Python and how to include quotes inside them.

Think about how you can mix quotes or use backslashes.

Describe the difference between normal strings and raw strings in Python.

Consider how \n behaves in each.

Practice

1. Which of the following is a correct way to create a string in Python?

easy

A. text = Hello'

B. text = Hello

C. text = 'Hello'

D. text = """Hello

Solution

1. Step 1: Check string delimiters

   Python strings must be enclosed in matching quotes: single ('') or double (\"\").

2. Step 2: Validate each option

   text = 'Hello' uses single quotes correctly. text = Hello misses quotes. text = Hello' has mismatched quotes. text = """Hello has unclosed triple quotes.

3. Final Answer:

   text = 'Hello' -> Option C

4. Quick Check:

   Strings need matching quotes = A [OK]

Hint: Strings always need matching quotes around text [OK]

Common Mistakes:

• Forgetting quotes around text
• Using mismatched quotes
• Leaving quotes unclosed

2. Which of the following is the correct syntax to create a multi-line string in Python?

easy

A. text = '''Hello
World'''

B. text = "Hello\nWorld"

C. text = 'Hello\nWorld'

D. text = '''Hello\nWorld'''

Solution

1. Step 1: Understand multi-line string syntax

   Triple quotes (''' or """) allow writing strings across multiple lines without escape characters.

2. Step 2: Analyze options

   Options A and B use single/double quotes with escaped newline, which works but is not multi-line string creation. text = '''Hello\nWorld''' uses triple quotes but escapes newline, so it shows literal \n. text = '''Hello World''' uses triple quotes with actual newline, creating a true multi-line string.

3. Final Answer:

   text = '''Hello World''' -> Option A

4. Quick Check:

   Triple quotes with real newlines = C [OK]

Hint: Use triple quotes and press Enter for multi-line strings [OK]

Common Mistakes:

• Using single or double quotes for multi-line text
• Escaping newlines inside triple quotes
• Confusing escaped \n with actual newlines

3. What will be the output of the following code?

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

medium

A. Hello\nWorld

B. Hello
World

C. Hello World

D. SyntaxError

Solution

1. Step 1: Understand triple-quoted string behavior

   Triple quotes preserve newlines inside the string as actual line breaks.

2. Step 2: Analyze the string content and print output

   The \n escape sequence in the triple-quoted string is interpreted as a newline character, so the string content is 'Hello' + newline + 'World'. Thus, print(text) outputs two lines: 'Hello' then 'World' on the next line.

3. Final Answer:

   Hello World (two lines) -> Option B

4. Quick Check:

   Triple quotes keep newlines = A [OK]

Hint: Triple quotes print newlines as line breaks, not \n text [OK]

Common Mistakes:

• Confusing escaped \n with actual newline
• Expecting literal \n to print as two characters
• Thinking triple quotes cause syntax error

4. The following code throws an error. What is the problem?

text = 'It's a sunny day'

medium

A. Missing escape for single quote inside string

B. Using double quotes instead of single quotes

C. Triple quotes needed for single quotes inside

D. No error, code is correct

Solution

1. Step 1: Identify the string delimiter and content

   The string uses single quotes to start and end, but contains an unescaped single quote inside (in "It's").

2. Step 2: Understand why error occurs

   The inner single quote ends the string early, causing a syntax error. It needs to be escaped with a backslash or use double/triple quotes.

3. Final Answer:

   Missing escape for single quote inside string -> Option A

4. Quick Check:

   Escape inner quotes or use different quotes = D [OK]

Hint: Escape inner quotes or use different quote types [OK]

Common Mistakes:

• Ignoring escape for inner quotes
• Assuming single quotes inside single quotes are allowed
• Not using triple quotes for complex strings

5. You want to create a dictionary where keys are words and values are their lengths from a multi-line string. Which code correctly creates this dictionary?

text = '''apple\nbanana\ncherry\n'''
# Fill in the blank:
d = {word: len(word) for word in _____}

hard

A. text.split()

B. text.split(' ')

C. text.split('\n')

D. text.splitlines()

Solution

1. Step 1: Understand the string and splitting methods

   The string ends with a newline ('''apple\nbanana\ncherry\n'''). splitlines() and split('\n') include a trailing empty string ''. split() splits on all whitespace (including newlines) and discards empty fields. split(' ') ignores newlines.

2. Step 2: Choose the method that avoids extra empty key

   split() produces exactly {'apple':5, 'banana':6, 'cherry':6} without '' : 0.

3. Final Answer:

   text.splitlines() -> Option D

4. Quick Check:

   splitlines() handles newlines cleanly = B [OK]

Hint: Use splitlines() to split on newlines cleanly [OK]

Common Mistakes:

• Using split() which discards empty lines but may split on other whitespace
• Using split('\n') which includes trailing empty string
• Using split(' ') which misses newlines