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Python 3中的字符串格式

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问题：Python 3中的字符串格式
回答 0
回答 1
回答 2
回答 3

问题：Python 3中的字符串格式

我在Python 2中执行此操作：

"(%d goals, $%d)" % (self.goals, self.penalties)

这是什么Python 3版本？

我尝试在线搜索示例，但一直在获取Python 2版本。

点击查看英文原文

I do this in Python 2:

"(%d goals, $%d)" % (self.goals, self.penalties)

What is the Python 3 version of this?

I tried searching for examples online but I kept getting Python 2 versions.

回答 0

这是有关“新”格式语法的文档。一个例子是：

"({:d} goals, ${:d})".format(self.goals, self.penalties)

如果goals和penalties均为整数（即​​默认格式为ok），则可以将其缩短为：

"({} goals, ${})".format(self.goals, self.penalties)

而且由于参数是的字段self，所以还有一种使用单个参数两次的方法（如@Burhan Khalid在评论中指出的那样）：

"({0.goals} goals, ${0.penalties})".format(self)

说明：

  • {} 表示仅下一个位置参数，采用默认格式；
  • {0}表示带有index的参数0，默认格式；
  • {:d} 是下一个位置参数，采用十进制整数格式；
  • {0:d}是带有index的参数0，十进制整数格式。

选择参数时，您可以执行许多其他操作（使用命名参数而不是位置参数，访问字段等），还有许多格式选项（填充数字，使用千位分隔符，显示或不显示符号等）。其他一些例子：

"({goals} goals, ${penalties})".format(goals=2, penalties=4)
"({goals} goals, ${penalties})".format(**self.__dict__)

"first goal: {0.goal_list[0]}".format(self)
"second goal: {.goal_list[1]}".format(self)

"conversion rate: {:.2f}".format(self.goals / self.shots) # '0.20'
"conversion rate: {:.2%}".format(self.goals / self.shots) # '20.45%'
"conversion rate: {:.0%}".format(self.goals / self.shots) # '20%'

"self: {!s}".format(self) # 'Player: Bob'
"self: {!r}".format(self) # '<__main__.Player instance at 0x00BF7260>'

"games: {:>3}".format(player1.games)  # 'games: 123'
"games: {:>3}".format(player2.games)  # 'games:   4'
"games: {:0>3}".format(player2.games) # 'games: 004'

注意：正如其他人指出的那样，新格式并不能取代前一种格式，这两种格式都可以在Python 3和更高版本的Python 2中使用。有人可能会说这是优先考虑的问题，但是恕我直言，较新的版本比旧的版本更具表现力，并且在编写新代码时应使用（当然，除非它针对较旧的环境）。

点击查看英文原文

Here are the docs about the “new” format syntax. An example would be:

"({:d} goals, ${:d})".format(self.goals, self.penalties)

If both goals and penalties are integers (i.e. their default format is ok), it could be shortened to:

"({} goals, ${})".format(self.goals, self.penalties)

And since the parameters are fields of self, there’s also a way of doing it using a single argument twice (as @Burhan Khalid noted in the comments):

"({0.goals} goals, ${0.penalties})".format(self)

Explaining:

  • {} means just the next positional argument, with default format;
  • {0} means the argument with index 0, with default format;
  • {:d} is the next positional argument, with decimal integer format;
  • {0:d} is the argument with index 0, with decimal integer format.

There are many others things you can do when selecting an argument (using named arguments instead of positional ones, accessing fields, etc) and many format options as well (padding the number, using thousands separators, showing sign or not, etc). Some other examples:

"({goals} goals, ${penalties})".format(goals=2, penalties=4)
"({goals} goals, ${penalties})".format(**self.__dict__)

"first goal: {0.goal_list[0]}".format(self)
"second goal: {.goal_list[1]}".format(self)

"conversion rate: {:.2f}".format(self.goals / self.shots) # '0.20'
"conversion rate: {:.2%}".format(self.goals / self.shots) # '20.45%'
"conversion rate: {:.0%}".format(self.goals / self.shots) # '20%'

"self: {!s}".format(self) # 'Player: Bob'
"self: {!r}".format(self) # '<__main__.Player instance at 0x00BF7260>'

"games: {:>3}".format(player1.games)  # 'games: 123'
"games: {:>3}".format(player2.games)  # 'games:   4'
"games: {:0>3}".format(player2.games) # 'games: 004'

Note: As others pointed out, the new format does not supersede the former, both are available both in Python 3 and the newer versions of Python 2 as well. Some may say it’s a matter of preference, but IMHO the newer is much more expressive than the older, and should be used whenever writing new code (unless it’s targeting older environments, of course).

回答 1

Python 3.6现在支持PEP 498的简写文字字符串插值。对于您的用例，新语法很简单：

f"({self.goals} goals, ${self.penalties})"

这与以前的.format标准，但让一个容易做的事情一样：

>>> width = 10
>>> precision = 4
>>> value = decimal.Decimal('12.34567')
>>> f'result: {value:{width}.{precision}}'
'result:      12.35'
点击查看英文原文

Python 3.6 now supports shorthand literal string interpolation with PEP 498. For your use case, the new syntax is simply:

f"({self.goals} goals, ${self.penalties})"

This is similar to the previous .format standard, but lets one easily do things like:

>>> width = 10
>>> precision = 4
>>> value = decimal.Decimal('12.34567')
>>> f'result: {value:{width}.{precision}}'
'result:      12.35'

回答 2

该行在Python 3中保持原样。

>>> sys.version
'3.2 (r32:88445, Oct 20 2012, 14:09:29) \n[GCC 4.5.2]'
>>> "(%d goals, $%d)" % (self.goals, self.penalties)
'(1 goals, $2)'
点击查看英文原文

That line works as-is in Python 3.

>>> sys.version
'3.2 (r32:88445, Oct 20 2012, 14:09:29) \n[GCC 4.5.2]'
>>> "(%d goals, $%d)" % (self.goals, self.penalties)
'(1 goals, $2)'

回答 3

我喜欢这种方法

my_hash = {}
my_hash["goals"] = 3 #to show number
my_hash["penalties"] = "5" #to show string
print("I scored %(goals)d goals and took %(penalties)s penalties" % my_hash)

请分别注意括号中的d和s。

输出将是：

I scored 3 goals and took 5 penalties
点击查看英文原文

I like this approach

my_hash = {}
my_hash["goals"] = 3 #to show number
my_hash["penalties"] = "5" #to show string
print("I scored %(goals)d goals and took %(penalties)s penalties" % my_hash)

Note the appended d and s to the brackets respectively.

output will be:

I scored 3 goals and took 5 penalties