I am reading through a python script that takes an input of XML files and outputs an XML file. However, I do not understand the printing syntax. Can someone please explain what f
in print(f"...")
does?
args = parser.parser_args() print(f"Input directory: {args.input_directory}") print(f"Output directory: {args.output_directory}")
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Answer
The f
means Formatted string literals and it’s new in Python 3.6
.
A formatted string literal or f-string is a string literal that is prefixed with
f
orF
. These strings may contain replacement fields, which are expressions delimited by curly braces{}
. While other string literals always have a constant value, formatted strings are really expressions evaluated at run time.
Some examples of formatted string literals:
>>> 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