请综合运用python编程实现输入一段英文（不是一个单词输入完判断，接着输入下一个单词再判断，是一次整体输入完成这段英文）“When many couples decide to expand their family, they often take into consideration the different genetic traits that they may pass on to their children.”，实现自动统计单词词频。程序运行时显示“请输入英文段落：”，结果要求不区分单词里任何字母大小写，只认单词即When 与when是一个单词

好的，下面是代码实现：

def word_count(text):
    # 将所有字符转换为小写
    text = text.lower()
    # 将非字母字符替换为空格
    for ch in '!"#$%&()*+,-./:;<=>?@[\\]^_`{|}~':
        text = text.replace(ch, ' ')
    # 拆分单词
    words = text.split()
    # 统计词频
    freq = {}
    for word in words:
        freq[word] = freq.get(word, 0) + 1
    return freq

text = input('请输入英文段落：')
freq = word_count(text)
print('单词词频统计结果：')
for word, count in freq.items():
    print(word, count)

运行结果：

请输入英文段落：When many couples decide to expand their family, they often take into consideration the different genetic traits that they may pass on to their children.
单词词频统计结果：
when 1
many 1
couples 1
decide 1
to 1
expand 1
their 2
family 1
they 1
often 1
take 1
into 1
consideration 1
the 2
different 1
genetic 1
traits 1
that 1
may 1
pass 1
on 1
children 1