什么是打印（f“…”）

Question

我正在阅读一个python脚本，该脚本接受XML文件的输入并输出XML文件。但是，我不了解打印语法。可有人请解释什么f的print(f"...")呢？

args = parser.parser_args()

print(f"Input directory: {args.input_directory}")
print(f"Output directory: {args.output_directory}")

Answer 1

该f方法格式化字符串字面量 和它的新功能Python 3.6。

甲 格式的字符串文字 或 F-串
是前缀字符串文字'f'或'F'。这些字符串可能包含替换字段，这些替换字段由花括号分隔{}。尽管其他字符串文字始终具有恒定值，但是格式化的字符串实际上是在运行时评估的表达式。

格式化字符串文字的一些示例：

>>> name = "Fred"
>>> f"He said his name is {name}."
"He said his name is Fred."

>>> name = "Fred"
>>> f"He said his name is {name!r}."
"He said his name is Fred."

>>> f"He said his name is {repr(name)}." # repr() is equivalent to !r
"He said his name is Fred."

>>> width = 10
>>> precision = 4
>>> value = decimal.Decimal("12.34567")
>>> f"result: {value:{width}.{precision}}" # nested fields
result: 12.35

>>> today = datetime(year=2017, month=1, day=27)
>>> f"{today:%B %d, %Y}" # using date format specifier
January 27, 2017

>>> number = 1024
>>> f"{number:#0x}" # using integer format specifier
0x400