Python提供四種主要字符串格式化方法：f-strings（推薦用於Python 3.6 ）、.format()方法（兼容舊版本）、%格式化（舊式，不推薦）和Template字符串（用於安全場(chǎng)景）；??其中f-strings因簡潔高效成為現(xiàn)代Python首選方法。

Formatting strings in Python is a common task, and there are several ways to do it depending on your needs and the Python version you're using. Here are the most widely used methods:

1. f-strings (Formatted String Literals) – Python 3.6

This is the most modern and recommended way. You prefix the string with f or F and include variables or expressions inside curly braces {} .

 name = "Alice"
age = 30
greeting = f"Hello, {name}. You are {age} years old."
print(greeting)
# Output: Hello, Alice. You are 30 years old.

You can also include expressions:

 price = 19.99
tax = 0.05
total = f"The total price with tax is ${price * (1 tax):.2f}."
print(total)
# Output: The total price with tax is $20.99.

The :.2f formats the number to two decimal places.

2. .format() method

This method works with older versions of Python and is still widely used. It uses placeholders {} that are replaced by arguments passed to .format() .

 name = "Bob"
age = 25
greeting = "Hello, {}. You are {} years old.".format(name, age)
print(greeting)
# Output: Hello, Bob. You are 25 years old.

You can also use positional or keyword arguments:

 greeting = "Hello, {name}. You are {age} years old.".format(name="Charlie", age=35)
print(greeting)

Or refer by index:

 info = "Name: {0}, Age: {1}, Name again: {0}".format("Dana", 28)
print(info)

3. % formatting (Old-style)

This is the oldest method, similar to C's printf. It uses %s , %d , %f , etc., as placeholders.

 name = "Eve"
age = 22
greeting = "Hello, %s. You are %d years old." % (name, age)
print(greeting)
# Output: Hello, Eve. You are 22 years old.

Common format specifiers:

• %s – string
• %d – integer
• %f – float
• %.2f – float with 2 decimal places

While it still works, it's generally discouraged in favor of f-strings or .format() .

4. Template strings (for simple cases or user input)

The string.Template class is useful when dealing with user-supplied formatting strings, as it's safer.

 from string import Template

t = Template("Hello, $name. You are $age years old.")
greeting = t.substitute(name="Frank", age=40)
print(greeting)
# Output: Hello, Frank. You are 40 years old.

This method is less common but good for cases where you want to avoid code injection risks in dynamic templates.

Each method has its place:

• Use f-strings for most modern code – they're fast, readable, and powerful.
• Use .format() when you need compatibility with older Python versions or more complex formatting logic.
• Avoid % formatting unless maintaining legacy code.
• Use Template for user-defined templates where security matters.

Basically, for new projects, go with f-strings unless you have a specific reason not to.

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