带有格式字符串和对象字面量的 Python SyntaxError

Question

This code produces SyntaxError :

f'something_{{ 'BEAM': '.', 'GRIN': '.', 'GRIN31': '/' }[coin]}'

Is it possible to use object literals this way for an inline "select"?

Answer 1

There are two problems.

First, you can't use single quotes in the dict display, because the string parser doesn't consider the braces to "separate" them; the first ' closes the string literal. (Or rather, you need to use different quotes or escape the quotes to avoid unintentionally closing the f-string.)

Second, {{ is a single literal { in an f-string; you need to separate them with a space.

>>> coin = "GRIN"
>>> f'something_{ { "BEAM": ".", "GRIN": ".", "GRIN31": "/" }[coin]}'
'something_.'

Answer 2

Yes, it's possible, here a example:

$ test1 = 'abc'
$ test2 = '123'
$ test3= 'foo'
$ coin = 'foo'
f"something_{ { test1: '.', test2: '.', test3: '/' }[coin]}"
>>> something_/

on f-string syntax, the brackets is represents by double {{ or }} => { or }, that's why first 2 { has an empty space between them.