如何使用 apply 或 map 将 Python for 循环编写为 lambda 函数？

Question

How would I write this code using a lambda function and apply or map? I have looked at several blog posts, etc., but for some reason I feel like I am missing something. I think it should be really simply.

for i in range(2,5):
    print(f'I only have {i} friends, but they are awesome.')

# I only have 2 friends, but they are awesome.
# I only have 3 friends, but they are awesome.
# I only have 4 friends, but they are awesome.

Answer 1

A loop is good enough for this task, but if for some reason you must use lambda and map, you can do it like this:

list(map(lambda x: print(f"I only have {x} friends, but they are awesome."), range(2, 5)))

The expression needs to be wrapped in list() as the map function is eagerly executed, which means it doesn't calculate the output until it is needed.

Answer 2

你不只是使用 lambda 或 map 来执行上面的代码，但是如果你只想用 lambda 或 map 来实现这一点，你需要将 map 对象转换为列表。

list(map(lambda x:print(f'I only have {x} friends, but they are awesome.'), range(2,5)))

Answer 3

You don't want to use lambdas at all, unreadable. Lambda expressions can't contain loops, statements. They can contain expressions only (think maths), However, Your problem can be approached like the following.

s = 'I only have {} friends, but they are awesome.'
f = lambda x: list(map(print, map(s.format, x)))
f([1, 2, 3])

We're calling list to force evaluate the result generator, note that it's called 3 times ([1, 2, 3]) and therefore, there're [None, None, None] returned. The result generator is basically mapping print function on a list that looks like [s.format(1), s.format(2), s.format(3)]

I wanted only to show you how to do it, but this is a very bad approach.

We can do the same with fstrings or percent %.