不在pandas中生成列表的空列表
不在pandas中生成列表的空列表
提问于 2019-06-05 08:10:59
背景
1)我有以下代码来创建df
import pandas as pd
word_list = ['crayons', 'cars', 'camels']
l = ['there are many different crayons in the bright blue box',
'i like a lot of sports cars because they go really fast',
'the middle east has many camels to ride and have fun']
df = pd.DataFrame(l, columns=['Text'])
df
Text
0 there are many different crayons in the bright blue box
1 i like a lot of sports cars because they go really fast
2 the middle east has many camels to ride and have fun2)，我有以下代码来创建一个函数
def find_next_words(row, word_list):
sentence = row[0]
# trigger words are the elements in the word_list
trigger_words = []
next_words = []
last_words = []
for keyword in word_list:
words = sentence.split()
for index in range(0, len(words) - 1):
if words[index] == keyword:
trigger_words.append(keyword)
#get the 3 words that follow trigger word
next_words.append(words[index + 1:index + 4])
#get the 3 words that come before trigger word
#DOES NOT WORK...PRODUCES EMPTY LIST
last_words.append(words[index - 1:index - 4])
return pd.Series([trigger_words, last_words, next_words], index = ['TriggerWords','LastWords', 'NextWords'])3)此函数使用上面的word_list中的单词来查找之前的和word_list中 "trigger_words"之后的的3个单词
4)然后我使用以下代码
df = df.join(df.apply(lambda x: find_next_words(x, word_list), axis=1))5)，并生成与我想要的非常接近的df
Text TriggerWords LastWords NextWords
0 there are many different crayons [crayons] [[]] [[in, the, bright]]
1 i like a lot of sports cars [cars] [[]] [[because, they, go]]
2 the middle east has many camels [camels] [[]] [[to, ride, and]] Problem
6)但是，LastWords列是列表[[]]的空列表。我认为问题出在上面的find_next_words函数中的这一行代码last_words.append(words[index - 1:index - 4])。
7)这让我有点困惑，因为NextWords列使用了非常相似的代码next_words.append(words[index + 1:index + 4])，取自find_next_words函数，并且它可以工作。
问题
8)如何修复我的代码，使其不生成列表[[]]的空列表，而是给出word_list中单词之前的3个单词
回答 1
Stack Overflow用户
回答已采纳
发布于 2019-06-05 08:26:26
我认为在代码中应该是words[max(index - 4, 0):max(index - 1, 0)]。
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原文链接：
https://stackoverflow.com/questions/56452788
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