collocations 函数使用过程中遇到 Error

Question

在直接上手使用《用 Python进行自然语言处理》一书中第39 页的例子时，出现了如下的ValueError，不知道什么情况，请大神帮忙解答，谢谢！

text4.collocations()
Traceback (most recent call last):
File "", line 1, in
text4.collocations()
File "/Users/jiamingxie/Library/Python/3.7/lib/python/site-packages/nltk/text.py", line 444, in collocations
w1 + " " + w2 for w1, w2 in self.collocation_list(num, window_size)
File "/Users/jiamingxie/Library/Python/3.7/lib/python/site-packages/nltk/text.py", line 444, in
w1 + " " + w2 for w1, w2 in self.collocation_list(num, window_size)
ValueError: too many values to unpack (expected 2)

Answer 1

for w1, w2 in self.collocation_list(num, window_size) 会解压一个含有两个元素的元组，too many values to unpack 提示后边的迭代部分每次返回的不是一个含有两个元素的元组，具体你打印出来看看