Python字符串格式化str.format()方法的实现

name = "Alice"
age = 30
message = "My name is {} and I am {} years old.".format(name, age)
print(message)

message = "My name is {0} and I am {1} years old.".format(name, age)

message = "My name is {name} and I am {age} years old.".format(name=name, age=age)

price = 49.95
formatted_price = "The price is {:.2f} dollars.".format(price)

# 左对齐
left_aligned = "{:<10}".format("Hello")
# 右对齐
right_aligned = "{:>10}".format("World")
# 居中对齐
center_aligned = "{:^10}".format("Python")
# 填充字符
filled = "{:*^10}".format("Text")

text = "Python"
left_aligned = "{:<10}".format(text)

text = "Python"
right_aligned = "{:>10}".format(text)

text = "Python"
center_aligned = "{:^10}".format(text)

value = 123.456789
formatted_value = "The value is {:.2f}".format(value)

number = 1234567
formatted_number = "Formatted number: {:,}".format(number)

percentage = 0.25
formatted_percentage = "Formatted percentage: {:.2%}".format(percentage)

from datetime import datetime

now = datetime.now()
formatted_date = "Current date and time: {:%Y-%m-%d %H:%M:%S}".format(now)

def custom_format(value):
    # 自定义格式化函数示例
    return f"Custom format: {value}"

data = "example"
formatted_data = custom_format(data)

items = [
    {"item": "Apple", "price": 0.5},
    {"item": "Banana", "price": 0.25},
    {"item": "Orange", "price": 0.75}
]

total = sum(item["price"] for item in items)

# 打印购物清单
print("Shopping List:")
for item in items:
    print("{item:<10} ${price:.2f}".format(**item))
print("-" * 20)
print("Total: ${:.2f}".format(total))