Python format 用法详解

一、填充字符串

1. 位置

print("hello {0}, this is {1}.".format("world", "python"))  # 根据位置下标进行填充
print("hello {}, this is {}.".format("world", "python"))  # 根据顺序自动填充
print("hello {0}, this is {1}. {1} is a new language.".format("world", "python"))  # 同一参数可以填充多次

输出：

hello world, this is python.
hello world, this is python.
hello world, this is python. python is a new language.

2. key

obj = "world"
name = "python"
print("hello {obj}, this is {name}.".format(obj = obj, name = name))

输出：

hello world, this is python.

3. 列表

list = ["world", "python"]
print("hello {names[0]}, this is {names[1]}.".format(names = list))

输出：

hello world, this is python.

4. 字典

dict = {"obj":"world", "name":"python"}
print("hello {names[obj]}, this is {names[name]}.".format(names = dict))

输出：

hello world, this is python.

注意：

访问字典的 key，不用引号。

5. 类属性

class Names():
    obj = "world"
    name = "python"

print("hello {names.obj}, this is {names.name}.".format(names = Names))

输出：

hello world, this is python.

6. 魔法参数

args = [",", "inx"]
kwargs = {"obj": "world", "name": "python"}
print("hello {obj}{} this is {name}.".format(*args, **kwargs))

输出：

hello world, this is python.

注意：

这里的 format(*args, **kwargs) 等价于 format(",", "inx", obj = "world", name = "python")。

二、数字格式化

三、其他用法

1. 转义

print("{{hello}} {{{0}}}".format("world"))

输出：

{hello} {world}

2. format 作为函数变量

name = "python"
hello = "hello, welcome to {} world!".format
print(hello(name))

输出：

hello, welcome to python world!

3. 格式化 datatime

from datetime import datetime
now = datetime.now()
print("{:%Y-%m-%d %X}".format(now))

输出：

2020-12-15 19:46:24

4. {}内嵌{}

print("hello {0:>{1}} ".format("world", 10))

输出：

hello      world

四、参考

python format 用法详解

Python format 格式化函数