Python：逆序打印输入（条件：只有字（至少4个字））

Question

I need to print input from the user in reverse order using a function. As a condition, just words (no floats/ int) should be allowed & at least four words need to be entered. eg: How can I help you --> you help I can How

It should'nt be possible to input: "4 5 6 7" or "There are 2 dogs" Here's my current code, however I didn't integrate that only strings are allowed so far:

def phrase():
    while True:
        user_input = input("Please insert a phrase: ")
        words = user_input.split(" ")
        n = len(words)
        if n >= 4:
            words = words[-1::-1]
            phrase_reverse = " ".join(words)
            print(phrase_reverse)
        else:
            print("Please only insert words and at least 4 ")
            continue
        break


phrase()

I tried with if n<4 and words == str: , if n<4 and words != string etc.. However, that didn't work. Could you please help me solving this issue? Maybe my code is wrong in general.

Answer 1

Reduce the problem to it's essential elements. The following should work - but your question looks suspiciously like homework.

    text = "test this for an example"  # use a text phrase to test.
    words = user_input.split().        # space is default for split.
    print(" ".join(reversed(words)))   # reverse list, and print as string.

result:

example an for this test

If you need to filter numerics..

    text = "test this for an 600 example" # use a text phrase to test.
    words = text.split()           # space is default for split.
    print(" ".join(reversed([wd for wd in words if not wd.isnumeric()])))
# filter, reverse, and print as string.

result:

example an for this test

If you need to reject numerics / responses with less than 4 words in a function.

def homework(text: str) -> bool:
    words = text.split()
    composed = list(reversed([wd for wd in words if not wd.isnumeric()]))
    result = len(words) == len(composed) and len(words) > 3
    if result:
        print(' '.join(composed))
    return result

Answer 2

It is a little bit nasty , but might be useful for you to check for nums: :)

inp = input()

try:
    int(inp)
except ValueError:
    # do your operations here