我将如何为 f 字符串对齐定义填充字符？

Question

我一直在搞乱文本对齐，包括字符串方法和 f 字符串。我当前的目标是创建 table 内容样式输出，看起来像这样：

Introduction....................1
Python Basics...................5
Creating Your First Program....12
Operators and Variables........29

很简单，我已经能够将其格式化为：

Introduction                    1
Python Basics                   5
Creating Your First Program    12
Operators and Variables        29

代码为：

for chapt, page in contents:
  print(f"{chapt:<30}{page:>5}")

我在网上找不到任何描述如何将填充字符和 f 字符串一起添加的资源。使用 .center、.ljust、.rjust 字符串方法，我已经能够做到这一点，因为它们采用宽度参数，然后是可选的填充字符。在上，我以为我找到了解决方案。

The x<y portion signifies to left-align the text with a width of y spaces. For any unused space, pad it with character x.

我尝试了这个方法，将我的打印语句从 print(f"{chapt:<30}{page:>5}") 编辑为 print(f"{chapt:'.'<30}{page:'.'>5}")。然而这 returns 一个错误：

Traceback (most recent call last):
  File "main.py", line 40, in <module>
    print(f"{chapt:'.'<30}{page:'.'>5}")
ValueError: Invalid format specifier

（第 40 行是我完整代码中的那一行。）

有什么方法可以选择填充字符，或者我是否必须恢复到字符串方法。我相信有，但我不知道如何使用它。谢谢！

Answer 1

在对齐字符（> 或 <）之前指定它，不带撇号。

contents = {"Introduction": 1, "Python Basics": 5, "Creating Your First Program": 12, "Operators and Variables": 29}
for chapt, page in contents.items():
    print(f"{chapt:.<30}{page:.>5}")

输出：

Introduction......................1
Python Basics.....................5
Creating Your First Program......12
Operators and Variables..........29

来自documentation

If a valid align value is specified, it can be preceded by a fill character that can be any character and defaults to a space if omitted. It is not possible to use a literal curly brace (“{” or “}”) as the fill character in a formatted string literal or when using the str.format() method. However, it is possible to insert a curly brace with a nested replacement field. This limitation doesn’t affect the format() function

Answer 2

根据Format Specification Mini-Language你必须在“对齐”之前指定它：

contents = [('Introduction', 1), ('Python Basics', 5),
            ('Creating Your First Program', 12),
            ('Operators and Variables', 29)]

row_length = 35

for chapt, page in contents:
    dots = str(row_length - len(str(page)))
    print(f"{chapt:.<{dots}}{page}")

*这现在与 page 的长度无关。更灵活一点。

我将如何为 f 字符串对齐定义填充字符？

How would I define a fill character for f-string alignment?

python

python-3.x

f-string