= (equal) 在表达式大括号内的 f 字符串中做什么? [英] What does = (equal) do in f-strings inside the expression curly brackets?

问题描述

众所周知，{} 在 Python f-strings 中的用法是执行代码段并以 string 格式给出结果(一些教程此处).但是，表达式末尾的="是什么意思?

log_file = open("log_aug_19.txt", "w")console_error = '...stuff...' # 真正的代码是用正则表达式生成的log_file.write(f'{console_error=')

解决方案

这实际上是一个 Python 3.8 的全新功能.

<块引用>

向 f 字符串添加了 = 说明符.一个 f 字符串，例如 f'{expr='将扩展到表达式的文本，一个等号，然后求值表达式的表示.

本质上，它促进了打印调试的频繁用例，因此，而我们通常必须编写:

f"some_var={some_var}"

我们现在可以写:

f"{some_var=}"

因此，作为演示，使用全新的 Python 3.8.0 REPL:

<预><代码>>>>打印(f{foo =}")富=42>>>

The usage of {} in Python f-strings is well known to execute pieces of code and give the result in string format (some tutorials here). However, what does the '=' at the end of the expression mean?

log_file = open("log_aug_19.txt", "w") 
console_error = '...stuff...'           # the real code generates it with regex
log_file.write(f'{console_error=}')

解决方案

This is actually a brand-new feature as of Python 3.8.

Added an = specifier to f-strings. An f-string such as f'{expr=}' will expand to the text of the expression, an equal sign, then the representation of the evaluated expression.

Essentially, it facilitates the frequent use-case of print-debugging, so, whereas we would normally have to write:

f"some_var={some_var}"

we can now write:

f"{some_var=}"

So, as a demonstration, using a shiny-new Python 3.8.0 REPL:

>>> print(f"{foo=}")
foo=42
>>>

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