How do I format a string using a dictionary in Python 3?

You can use dictionaries to format strings in Python using several methods. The most common approaches are %-formatting, str.format(), and f-strings. Each method allows you to insert dictionary values into string templates.

Using %-formatting with Dictionaries

The traditional method uses % operator with dictionary keys in parentheses ?

data = {'language': 'Python', 'number': 2, 'cost': 99.99}

# Basic string interpolation
result = '%(language)s has %(number)03d quote types.' % data
print(result)

# Formatting numbers
price = 'The course costs $%(cost).2f' % data
print(price)

Python has 002 quote types.
The course costs $99.99

Using str.format() with Dictionaries

The str.format() method provides more flexibility and readability ?

data = {'name': 'Alice', 'age': 30, 'score': 95.7}

# Using dictionary unpacking
result = "Name: {name}, Age: {age}, Score: {score:.1f}".format(**data)
print(result)

# Direct dictionary access
result2 = "Hello {0[name]}, you scored {0[score]:.2f}%".format(data)
print(result2)

Name: Alice, Age: 30, Score: 95.7
Hello Alice, you scored 95.70%

Using f-strings (Recommended)

F-strings (Python 3.6+) offer the cleanest and most readable syntax ?

data = {'product': 'Laptop', 'price': 1299.99, 'quantity': 5}

# Direct dictionary access in f-strings
result = f"Product: {data['product']}, Price: ${data['price']:.2f}"
print(result)

# Multiple values
summary = f"Order: {data['quantity']} x {data['product']} = ${data['price'] * data['quantity']:.2f}"
print(summary)

Product: Laptop, Price: $1299.99
Order: 5 x Laptop = $6499.95

Comparison

Conclusion

Use f-strings for modern Python code as they're fastest and most readable. Use str.format() for older Python versions or complex formatting needs. The % operator is legacy but still widely supported.