仅仅

a = 10.1234
print(f"{a:.1f}")

输出：10.1

a = 10.1234
print(f"{a:.2f}")

输出：10.12

a = 10.1234
print(f"{a:.3f}")

输出：10.123

a = 10.1234
print(f"{a:.4f}")

输出：10.1234

只需更改小数点符号后的值，小数点符号表示您要打印的小数点。

a = 10.1234

print(f"{a:0.2f}")

在0.2f中：

0告诉python不限制陈列.2表示我们只想在小数后取2位（结果将与round（）函数相同）f表示它是一个浮点数。如果你忘记了f，那么它只会在小数点后少打印1个数字。在这种情况下，它只能是小数后1位。

关于数字f-string的详细视频https://youtu.be/RtKUsUTY6to?t=606

仅仅

a = 10.1234
print(f"{a:.1f}")

输出：10.1

a = 10.1234
print(f"{a:.2f}")

输出：10.12

a = 10.1234
print(f"{a:.3f}")

输出：10.123

a = 10.1234
print(f"{a:.4f}")

输出：10.1234

只需更改小数点符号后的值，小数点符号表示您要打印的小数点。

Consider:

>>> number1 = 10.1234
>>> f'{number1:.2f}'
'10.12'

Syntax:

"{" [field_name] ["!" conversion] [":" format_spec] "}"

Explanation:

# Let's break it down...
#       [field_name]     => number1
#       ["!" conversion] => Not used
#       [format_spec]    => [.precision][type] 
#                        => .[2][f] => .2f  # where f means Fixed-point notation

---

更进一步，Format字符串具有以下语法。正如你所看到的，还有很多事情可以做。

Syntax: "{" [field_name] ["!" conversion] [":" format_spec] "}"

# let's understand what each field means...
    field_name        ::=  arg_name ("." attribute_name | "[" element_index "]")*
    arg_name          ::=  [identifier | digit+]
    attribute_name    ::=  identifier
    element_index     ::=  digit+ | index_string
    index_string      ::=  <any source character except "]"> +
    conversion        ::=  "r" | "s" | "a"
    format_spec       ::=  [[fill]align][sign][#][0][width][grouping_option][.precision][type]

            # Looking at the underlying fields under format_spec...
            fill            ::=  <any character>
            align           ::=  "<" | ">" | "=" | "^"
            sign            ::=  "+" | "-" | " "
            width           ::=  digit+
            grouping_option ::=  "_" | ","
            precision       ::=  digit+
            type            ::=  "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"

---

参考https://docs.python.org/3/library/string.html#format-字符串语法

添加到Rob的答案中，您可以将格式说明符与f字符串一起使用（这里有更多）。

您可以控制小数位数：

pi = 3.141592653589793238462643383279

print(f'The first 6 decimals of pi are {pi:.6f}.')

The first 6 decimals of pi are 3.141593.

您可以转换为百分比：

grade = 29/45

print(f'My grade rounded to 3 decimals is {grade:.3%}.')

My grade rounded to 3 decimals is 64.444%.

您可以执行其他操作，如打印恒定长度：

from random import randint
for i in range(5):
    print(f'My money is {randint(0, 150):>3}$')

My money is 126$
My money is   7$
My money is 136$
My money is  15$
My money is  88$

或甚至使用逗号千分隔符打印：

print(f'I am worth {10000000000:,}$')

I am worth 10,000,000,000$

添加到Robᵩ's回答：如果你想打印相当大的数字，使用千个分隔符可以是一个很大的帮助（注意逗号）。

>>> f'{a*1000:,.2f}'
'10,123.40'

如果您想填充/使用固定宽度，则宽度在逗号之前：

>>> f'{a*1000:20,.2f}'
'           10,123.40'