python - Pandas - 将数据附加到特定列

Question

我需要将列表中的数据附加到特定列。我有 4 个列表:

orderNumber = ['123456789']
countryOfOrigin = ['United Kingdom']
sizeList = ['2', '4']
quantityList = ['10', '12']

我还有一个包含以下标题的 CSV 文件:

OrderNumber   COO   Size   QTY

我需要将这些列表附加到此 CSV 的正确列中。如果列表中只有一项数据，则只需复制以填充所有行

OrderNumber        COO         Size   QTY
123456789     United Kingdom    2     10
123456789     United Kingdom    4     20

这是我试过的。但它所做的一切都是在同一列中将所有内容逐一添加

orderNumber = ['123456789']
countryOfOrigin = ['United Kingdom']
sizeList = ['2', '4']
quantityList = ['10', '12']

header = ["OrderNumber", "COO", "Size", "QTY"]
order = pd.DataFrame(orderNumber)
order.to_csv('C:/Users/user/Desktop/Pandas-Example2.csv', mode='a', index=False)
size = pd.DataFrame(sizeList, columns=["Size"])
size.to_csv('C:/Users/user/Desktop/Pandas-Example2.csv', mode='a', index=False)

知道如何解决这个问题吗？

Answer 1

如果可能的话，使用一个元素只列出标量，创建标量/列表的字典并传递给 DataFrame 构造函数——所有列表必须具有相同的长度:

orderNumber = '123456789'
countryOfOrigin = 'United Kingdom'
sizeList = ['2', '4']
quantityList = ['10', '12']

d = {"OrderNumber": orderNumber, "COO":countryOfOrigin, "Size":sizeList, "QTY":quantityList}
order = pd.DataFrame(d)
print (order)
  OrderNumber             COO Size QTY
0   123456789  United Kingdom    2  10
1   123456789  United Kingdom    4  12

如果输入总是列表，你可以使用一些预处理:

orderNumber = ['123456789']
countryOfOrigin = ['United Kingdom']
sizeList = ['2', '4']
quantityList = ['10', '12']

vals = [orderNumber, countryOfOrigin, sizeList, quantityList]
header = ["OrderNumber", "COO", "Size", "QTY"]

d = {a: b[0] if len(b) == 1 else b for a, b in zip(header, vals)}
order = pd.DataFrame(d)
print (order)
  OrderNumber             COO Size QTY
0   123456789  United Kingdom    2  10
1   123456789  United Kingdom    4  12