嵌套for循环扩展现有lis

Question

给我解释一下这个代码。这是一个以字母形式输出整数输入的程序。如果我输入35，那么输出将是35。我了解其中的大部分内容，但想知道如何从

twenty thirty forty fifty sixty seventy eighty ninety

代码是：

num = int(input("Enter the number:"))
numbers = ("zero one two three four five six seven eight nine".split())
numbers.extend("ten eleven twelve thirteen fourteen fifteen sixteen".split())
numbers.extend("seventeen eighteen nineteen".split())
numbers.extend(tens if ones == "zero" else (tens + " " + ones) 
    for tens in "twenty thirty forty fifty sixty seventy eighty ninety".split()
    for ones in numbers[0:10])

print(numbers[num])

Answer 1

您在最后一行中看到的两个主要概念是list comprehension和nested loops。看一看。你知道吗

为了更好地理解正在发生的事情，我们将把这条线分成更简单的部分：

十位数

for tens in "twenty thirty forty fifty sixty seventy eighty ninety".split():
    print(tens)

OUTPUT: twenty thirty forty fifty sixty seventy eighty ninety

前面的for循环对应于列表中的以下内容：

(tens for tens in "twenty thirty forty fifty sixty seventy eighty ninety".split())

不带print，返回生成器。如果要查看结果：

print(list(tens for tens in "twenty thirty forty fifty sixty seventy eighty ninety".split()))

个

numbers = ("zero one two three four five six seven eight nine".split())
for ones in numbers[0:10]:
    print(ones)

OUTPUT: zero one two three four five six seven eight nine

前面的for循环对应于列表中的以下内容：

    (ones for ones in numbers[0:10])

为循环合并

我们可以合并它们：

for tens in "twenty thirty forty fifty sixty seventy eighty ninety".split():
    for ones in numbers[0:10]:
        print(tens + " " + ones)
OUTPUT: twenty zero
twenty one
twenty two
twenty three
twenty four
twenty five
twenty six
twenty seven
twenty eight
twenty nine
thirty zero
thirty one
thirty two
[...]

因为我们不太喜欢twenty zero，所以我们要添加一个子句：

for tens in "twenty thirty forty fifty sixty seventy eighty ninety".split():
    for ones in numbers[0:10]:
        if ones == "zero":
            print(tens)
        else:
            print(tens + " " + ones)
OUTPUT:
twenty
twenty one
twenty two
twenty three
twenty four
[...]

这和列表理解是一样的：

(tens if ones == "zero" else (tens + " " + ones) for tens in "twenty thirty forty fifty sixty seventy eighty ninety".split() for ones in numbers[0:10])

它返回一个列表（*generator），该列表将扩展到numbers列表。
最后，您输入的数字对应于列表中单词的索引