Python 3.6 中带元组的格式化字符串文字 [英] Formatted string literals in Python 3.6 with tuples
问题描述
使用 str.format()
我可以使用元组来访问参数:
或
<预><代码>>>>t = ('a', 'b', 'c')>>>'{0}, {1}, {2}'.format(*t)'a, b, c'但是对于以f"(f 字符串)为前缀的新格式化字符串文字,我该如何使用元组?
f'{0}, {1}, {2}'.(*t) # 不起作用
你的第一个 str.format()
调用是一个带有 3 个参数的常规方法调用,那里没有涉及元组.您的第二个调用使用 *
splat 调用语法;str.format()
调用接收 3 个单独的参数,它不在乎那些来自元组.
使用 f
格式化字符串不使用方法调用,因此您不能使用任何一种技术.f'..'
格式化字符串中的每个插槽都作为正则 Python 表达式执行.
您必须直接从元组中提取您的值:
f'{t[0]}, {t[1]}, {t[2]}'
或者首先将元组扩展为新的局部变量:
a, b, c = tf'{a}, {b}, {c}'
或者干脆继续使用str.format()
.您不必使用 f'..'
格式化字符串,这是该语言的新附加功能,而不是替换 str.format()
.
本 PEP 不建议删除或弃用任何现有的字符串格式机制.
With str.format()
I can use tuples for accesing arguments:
>>> '{0}, {1}, {2}'.format('a', 'b', 'c')
'a, b, c'
or
>>> t = ('a', 'b', 'c')
>>> '{0}, {1}, {2}'.format(*t)
'a, b, c'
But with the new formatted string literals prefixed with 'f' (f-strings), how can I use tuples?
f'{0}, {1}, {2}'.(*t) # doesn't work
Your first str.format()
call is a regular method call with 3 arguments, there is no tuple involved there. Your second call uses the *
splat call syntax; the str.format()
call receives 3 separate individual arguments, it doesn't care that those came from a tuple.
Formatting strings with f
don't use a method call, so you can't use either technique. Each slot in a f'..'
formatting string is instead executed as a regular Python expression.
You'll have to extract your values from the tuple directly:
f'{t[0]}, {t[1]}, {t[2]}'
or first expand your tuple into new local variables:
a, b, c = t
f'{a}, {b}, {c}'
or simply continue to use str.format()
. You don't have to use an f'..'
formatting string, this is a new, additional feature to the language, not a replacement for str.format()
.
From PEP 498 -- Literal String Interpolation:
This PEP does not propose to remove or deprecate any of the existing string formatting mechanisms.
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