What does python’s format function mean?

Starting from Python 2.6, a new function str.format() for formatting strings has been added, which enhances the function of string formatting.

The basic syntax is to use {} and : to replace the previous %.

The format function can accept unlimited parameters, and the positions do not need to be in order.

format format function

Example

>>>"{} {}".format("hello", "world")    # 不设置指定位置，按默认顺序
'hello world'
 >>> "{0} {1}".format("hello", "world")  # 设置指定位置
'hello world'
 >>> "{1} {0} {1}".format("hello", "world")  # 设置指定位置
'world hello world'

You can also set parameters:

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Example

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 print("网站名：{name}, 地址 {url}".format(name="php中文网", url="www.php.cn"))
 # 通过字典设置参数
site = {"name": "php中文网", "url": "www.php.cn"}
print("网站名：{name}, 地址 {url}".format(**site))
 # 通过列表索引设置参数
my_list = ['php中文网', 'www.php.cn']
print("网站名：{0[0]}, 地址 {0[1]}".format(my_list))  # "0" 是必须的

The output result is:

网站名：php中文网, 地址 www.php.cn
网站名：php中文网, 地址 www.php.cn 
网站名：php中文网, 地址 www.php.cn

You can also pass in objects to str.format() ：

Example

#!/usr/bin/python# 
-*- coding: UTF-8 -*-
class AssignValue(object):    
    def __init__(self, value):        
        self.value = value
my_value = AssignValue(6)
print('value 为: {0.value}'.format(my_value))  # "0" 是可选的

The output result is:

value 为: 6

Number formatting

The following table shows str.format() Various ways to format numbers:

>>> print("{:.2f}".format(3.1415926));
3.14

In addition, we can use braces {} to escape braces, as shown in the following example:

Example

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 print ("{} 对应的位置是 {{0}}".format("php"))

The output result is:

php and the corresponding position is {0}

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