在这种情况下,如何在Python中使用replace()函数?

切片字符串并仅在您感兴趣的切片上替换,重建字符串。

>>> s = "Land grade 4 year 3 4 members at building 4"
>>> s[0:20]+s[20:24].replace("4","3.5")+s[24:]
'Land grade 4 year 3 3.5 members at building 4'

如果只更换一个,可能会稍微好一点,这样可以避免字符串切片:

>>> s[0:20]+s[20:].replace("4","3.5",1)
'Land grade 4 year 3 3.5 members at building 4'

但是如果你确切地知道要替换的数字在哪里,那可能是因为你可以用一个模板字符串来替换。

s = "Land grade 4 year 3 {} members at building 4"
s.format(3.5)