Card 14: Strings

Module 6: Advanced Techniques

1 The Hook

Think of a String like a bead necklace.

Indexing: Picking ONE bead.
Slicing: Cutting a SECTION of the necklace.

Computers start counting from 0, not 1!

2 Worked Example

Extracting parts of a secret code.

# P=0, Y=1, T=2, H=3, O=4, N=5

code = "PYTHON"

# Index [0] gets First

print(code[0]) # Prints "P"

# Slice [0:3] gets 0, 1, 2 (Stops BEFORE 3)

print(code[0:3]) # Prints "PYT"

Power Up: Left & Right

You might see exam questions ask for LEFT or RIGHT characters.

# LEFT(3) -> First 3

text[:3] // Start at 0, stop at 3

# RIGHT(3) -> Last 3

text[-3:] // Start at -3, go to end

PREDICT

What is the output?

word = "GALAXY"
print(word[1])

Remember: G is 0, A is 1...

Interactive Editor

main.py

agent = "James Bond"
# Indexing
print(agent[0])
# Slicing (Includes 0, 1, 2, 3, 4. STOPS at 5)
print(agent[0:5])
# Negative Indexing (Last one)
print(agent[-1])

Terminal Output

> _

BRONZE (MODIFY)

🥉 Last Letter

1. The code currently prints the FIRST letter [0].
2. Change it to print the LAST letter using [-1].
3. Run it to see "n".

bronze.py

word = "Python"
print(word[0])

> _

SILVER (FIX)

🥈 Off by One Error

1. The goal is to extract "Code" (first 4 letters).
2. The code uses [0:3] which only gives indices 0, 1, 2.
3. Fix it to include index 3. Hint: Stop number is NOT included!

silver.py

text = "Codebreaker"
# Needs to print "Code"
print(text[0:3])

> _

GOLD (MAKE)

🥇 User Gen

1. Ask for first name.
2. Ask for last name.
3. Create username: First 3 letters of first + First 2 of last.
4. Print it in UPPERCASE.

gold.py

first = input("First: ")
last = input("Last: ")

# Combine
user = ...
print(...)

> _

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