详解Python3 中的字符串格式化语法

脚本专栏 2024/11/19 佚名

2 0 1

神剑山庄资源网 Design By www.hcban.com

一、旧式的字符串格式化

% 操作符

参考以下示例：

> name = "Eric"
> "Hello, %s." % name
'Hello, Eric.'

当有多个变量需要插入到字符串中时：

> name = "Eric"
> age = 74
> "Hello, %s. You are %s." % (name, age)
'Hello, Eric. You are 74.'

当需要替换的变量进一步增多时，使用 % 操作符格式化字符串会导致代码可读性变得很差：

> first_name = "Eric"
> last_name = "Idle"
> age = 74
> profession = "comedian"
> affiliation = "Monty Python"
> "Hello, %s %s. You are %s. You are a %s. You were a member of %s." % (first_name, last_name, age, profession, affiliation)
'Hello, Eric Idle. You are 74. You are a comedian. You were a member of Monty Python.'

str.format()

str.format() 是对 % 方式的改进，它使用常见的函数调用的语法，并且可以通过定义对象本身的 __format__() 方法控制字符串格式化的具体行为。

基本用法：

> name = "Eric"
> age = 74
> "Hello, {}. You are {}.".format(name, age)
'Hello, Eric. You are 74.'

str.format() 相对于 % 操作符有着更强的灵活性。比如可以通过数字索引来关联替换到字符串中的变量：

> name = "Eric"
> age = 74
> "Hello, {1}. You are {0}.".format(age, name)
'Hello, Eric. You are 74.'

为了提高代码可读性， {} 中也可以使用有具体含义的参数名：

> name = "Eric"
> age = 74
> "Hello, {name}. You are {age}".format(name=name, age=age)
'Hello, Eric. You are 74'

针对字典结构的数据：

> person = {'name': 'Eric', 'age': 74}
> "Hello, {name}. You are {age}.".format(name=person['name'], age=person['age'])
'Hello, Eric. You are 74.'

或者更简洁的方式：

> person = {'name': 'Eric', 'age': 74}
> "Hello, {name}. You are {age}.".format(**person)
'Hello, Eric. You are 74.'

问题在于当需要替换的变量很多时， str.format() 方式依然会导致代码变得过于冗长：

> first_name = "Eric"
> last_name = "Idle"
> age = 74
> profession = "comedian"
> affiliation = "Monty Python"
> "Hello, {first_name} {last_name}. You are {age}.  You are a {profession}. You were a member of {affiliation}." .format(first_name=first_name, last_name=last_name, age=age,  profession=profession, affiliation=affiliation)
'Hello, Eric Idle. You are 74. You are a comedian. You were a member of Monty Python.'

二、f-string

基本用法

> name = "Eric"
> age = 74
> f"Hello, {name}. You are {age}."
'Hello, Eric. You are 74.'

嵌入表达式

> f"{2 * 37}"
'74'

> def to_lowercase(input):
...  return input.lower()
 
> name = "Eric Idle"
> f"{to_lowercase(name)} is funny"
'eric idle is funny'

> f"{name.lower()} is funny"
'eric idle is funny'

f-string 中还可以直接嵌入某个对象实例，只要其内部实现了 __str__ 或者 __repr__ 方法：

class Comedian:
 def __init__(self, first_name, last_name, age):
  self.first_name = first_name
  self.last_name = last_name
  self.age = age

 def __str__(self):
  return f"{self.first_name} {self.last_name} is {self.age}"


new_comedian = Comedian("Eric", "Idle", 74)
print(f"{new_comedian}")
# Eric Idle is 74
多行 f-string
> name = "Eric"
> profession = "comedian"
> affiliation = "Monty Python"
> message = (
...  f"Hi {name}. "
...  f"You are a {profession}. "
...  f"You were in {affiliation}."
... )
> message
'Hi Eric. You are a comedian. You were in Monty Python.'

总结

以上所述是小编给大家介绍的Python3 中的字符串格式化语法，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！
如果你觉得本文对你有帮助，欢迎转载，烦请注明出处，谢谢！

Python3,格式化字符串,python字符串格式化

标签：

Python3,格式化字符串,python字符串格式化

神剑山庄资源网 Design By www.hcban.com

神剑山庄资源网 免责声明：本站文章均来自网站采集或用户投稿，网站不提供任何软件下载或自行开发的软件！如有用户或公司发现本站内容信息存在侵权行为，请邮件告知！ 858582#qq.com

神剑山庄资源网 Design By www.hcban.com

评论“详解Python3 中的字符串格式化语法”

暂无详解Python3 中的字符串格式化语法的评论...

www.hcban.com 神剑山庄资源网

139,976影音资源

144,792福利资源

21,817软件资源

631,128技术资源

详解Python3 中的字符串格式化语法

Python3,格式化字符串,python字符串格式化

Pytorch中的VGG实现修改最后一层FC

用pytorch的nn.Module构造简单全链接层实例

评论“详解Python3 中的字符串格式化语法”

稳了！魔兽国服回归的3条重磅消息！官宣时间再确认！

更新日志

友情链接