Chapter 15: Format Specifiers¶

🚀 Open Notebook¶

📺 Video Tutorial¶

Learn Python format specifiers in 5 minutes! 💬 (5:32)

📚 What You’ll Learn¶

Master advanced string formatting to display numbers, prices, and data professionally!

🎯 Learning Objectives¶

Use format specifiers with f-strings
Control decimal places and rounding
Align text and numbers
Format currencies and percentages

📖 Concept Explanation¶

Format specifiers control how values are displayed in f-strings using the syntax {value:specifier}.

Common Format Specifiers¶

Specifier	Description	Example	Output
`:.2f`	2 decimal places	`{3.14159:.2f}`	`3.14`
`:10`	Width of 10	`{42:10}`	`42`
`:>10`	Right align	`{42:>10}`	`42`
`:<10`	Left align	`{42:<10}`	`42`
`:^10`	Center align	`{42:^10}`	`42`
`:05`	Zero padding	`{42:05}`	`00042`
`:,`	Thousands separator	`{1000:,}`	`1,000`
`:+`	Show sign	`{42:+}`	`+42`
`:%`	Percentage	`{0.75:%}`	`75.000000%`
`:.1%`	Percentage (1 decimal)	`{0.756:.1%}`	`75.6%`

💡 Examples¶

Decimal Places¶

pi = 3.14159265
print(f"{pi:.2f}")    # 3.14
print(f"{pi:.4f}")    # 3.1416
print(f"{pi:.0f}")    # 3

Alignment and Width¶

name = "Python"
price = 19.99

print(f"{name:>10}")  # "    Python" (right aligned)
print(f"{name:<10}")  # "Python    " (left aligned)
print(f"{name:^10}")  # "  Python  " (centered)
print(f"{price:>10.2f}")  # "     19.99"

Thousands Separator¶

population = 7800000000
print(f"{population:,}")  # 7,800,000,000

price = 1234.56
print(f"${price:,.2f}")   # $1,234.56

Zero Padding¶

number = 42
print(f"{number:05}")  # 00042
print(f"{number:03}")  # 042

# Useful for IDs
user_id = 7
print(f"USER-{user_id:04}")  # USER-0007

✍️ Practice Exercises¶

Format price to 2 decimals with dollar sign
Create aligned table of names and scores
Format phone number with zero padding
Display large numbers with comma separators
Show percentages with 1 decimal place
Create formatted invoice

🎮 Real-World Examples¶

Price List¶

items = [
    ("Apple", 0.99),
    ("Banana", 0.59),
    ("Orange", 1.29)
]

print("ITEM       | PRICE")
print("-" * 20)
for item, price in items:
    print(f"{item:<10} | ${price:>5.2f}")

# Output:
# ITEM       | PRICE
# --------------------
# Apple      | $ 0.99
# Banana     | $ 0.59
# Orange     | $ 1.29

Financial Report¶

revenue = 1234567.89
expenses = 987654.32
profit = revenue - expenses

print("FINANCIAL REPORT")
print("=" * 30)
print(f"Revenue:  ${revenue:>12,.2f}")
print(f"Expenses: ${expenses:>12,.2f}")
print(f"Profit:   ${profit:>12,.2f}")

# Output:
# FINANCIAL REPORT
# ==============================
# Revenue:  $ 1,234,567.89
# Expenses: $   987,654.32
# Profit:   $   246,913.57

Progress Display¶

completed = 75
total = 100
percentage = completed / total

print(f"Progress: {percentage:.1%}")  # Progress: 75.0%
print(f"Completed: {completed}/{total}")
print(f"[{'=' * completed}{' ' * (total-completed)}] {percentage:.0%}")
# [===========================================================================                         ] 75%

Student Grades¶

students = [
    ("Alice", 95.5),
    ("Bob", 87.3),
    ("Charlie", 92.8)
]

print(f"{'Name':<10} | {'Grade':>5} | {'Letter'}")
print("-" * 30)
for name, grade in students:
    letter = "A" if grade >= 90 else "B" if grade >= 80 else "C"
    print(f"{name:<10} | {grade:>5.1f} | {letter}")

# Output:
# Name       | Grade | Letter
# ------------------------------
# Alice      |  95.5 | A
# Bob        |  87.3 | B
# Charlie    |  92.8 | A

📝 Advanced Formatting¶

Scientific Notation¶

big_number = 1000000
print(f"{big_number:e}")   # 1.000000e+06
print(f"{big_number:.2e}") # 1.00e+06

Binary, Octal, Hex¶

number = 255
print(f"{number:b}")   # 11111111 (binary)
print(f"{number:o}")   # 377 (octal)
print(f"{number:x}")   # ff (hexadecimal lowercase)
print(f"{number:X}")   # FF (hexadecimal uppercase)

Custom Separators¶

number = 1234567
print(f"{number:_}")     # 1_234_567
print(f"{number:,}")     # 1,234,567

🚀 Challenge Projects¶

Receipt Generator: Create formatted receipts with items and prices
Grade Report Card: Display student names, scores, and letter grades aligned
Financial Dashboard: Show revenue, expenses, profit with proper formatting
Time Display: Format seconds into HH:MM:SS with zero padding
Product Catalog: Create aligned product catalog with prices

🎓 Key Takeaways from Video¶

Strings are text data enclosed in quotes
Follow along with the video for hands-on practice
Experiment with the code examples to deepen understanding

💡 These points cover the main concepts from the video tutorial to help reinforce your learning.

🔗 Next Chapter¶

Continue to Chapter 16: While Loops to learn about repetition and iteration!