如何持續添加列表到另一個在python

Question

我知道如何在Python中添加數組彼此，但我很困惑如何不斷擴展數組。

#import numpy as np 
import matplotlib.pyplot as plt 
import xlrd 

path = r"C:\Users\berro\Documents\Sample Excel and CSV Files\shoesize.xls" 

book = xlrd.open_workbook(path) 
#print(book.nsheets) 
#print(book.sheet_names()) 

sheet = book.sheet_by_index(0) 

print(sheet.row_values(1,2,4)) 


for x in range (1,11): 
    trainX = [sheet.row_values(x,2,4)] 
    trainX.extend([sheet.row_values(x+1,2,4)]) 

print(trainX) 


trainX.append(sheet.row_values(2, 2, 4)) 
trainX.append(sheet.row_values(4,2,4)) 
trainX.append(sheet.row_values(5,2,4)) 
trainX.append(sheet.row_values(6,2,4)) 
trainX.append(sheet.row_values(7,2,4)) 
trainX.append(sheet.row_values(8,2,4)) 
trainX.append(sheet.row_values(9,2,4)) 
print(trainX) 




#shoe size, height 
features = [[sheet.row_values(1,2,4),sheet.row_values(2,2,4)]] 

我是一些Python的新手，但我很難找到一種迭代的方式來將trainX數組擴展到我想要的長度。

Answer 1

for x in range (1,11): 
    trainX = [sheet.row_values(x,2,4)] 
    trainX.extend([sheet.row_values(x+1,2,4)]) 

這將覆蓋trainX在每個迭代上，所以最後你只會在那裏有兩個元素。所以你需要在循環之外創建trainX，然後繼續添加它。

請注意，如果您只是在每次迭代中添加一個元素，則不需要擴展。可以保持append然後：

# create an empty list first 
trainX = [] 

# start at index 1, end at index 9 (inclusive; or exclusive 10) 
for x in range (1, 10): 
    trainX.append(sheet.row_values(x, 2, 4))