Question

我正在尝试让我的阵列打印其所有元素，但仅产生一个元素。 ive尝试注释掉“ for row”部分的不同部分，并表明它们可以正常工作。它将永远只是一个。任何帮助，将不胜感激，谢谢。

            wA = csv.reader(warehouse_A)
            next(wA, None) ## skips the header
            wB = csv.reader(warehouse_B)
            next(wB, None) ## skips the header
            wC = csv.reader(warehouse_C)
            next(wC, None) ## skips the header
            wD = csv.reader(warehouse_D)
            next(wD, None) ## skips the header


            a_itemno = []           ## empty arrays for the item number of the warehouse to be placed
            a_descripton = []               ## empty arrays for the item descripton of the warehouse to be placed
            a_value = []            ## empty arrays for the item value of the warehouse to be placed

            b_itemno = []           
            b_descripton = []               
            b_value = []            

            c_itemno = []           
            c_descripton = []               
            c_value = []            

            d_itemno = []           
            d_descripton = []               
            d_value = []            


            for row in wA:   ## places the 1st row on the spreadsheets into a new array
            a_itemno.append(row[0])

            for row in wB:
            b_itemno.append(row[0])

            for row in wC:
            c_itemno.append(row[0])

            for row in wD:
            d_itemno.append(row[0])


            for row in wA:   ## places the 2rd row on the spreadsheets into a new array
            a_descripton.append(row[1])

            for row in wB:
            b_descripton.append(row[1])

            for row in wC:
            c_descripton.append(row[1])

            for row in wD:
            d_descripton.append(row[1])


            for row in wA:   ## places the 3rd row on the spreadsheets into a new array
            a_value.append(row[2])

            for row in wB:
            b_value.append(row[2])

            for row in wC:
            c_value.append(row[2])

            for row in wD:
            d_value.append(row[2])


            new_wA = [[a_itemno], [a_descripton], [a_value]] ## new array that only prints one element

            print (new_wA)

我正在寻找的输出将是： [[[[blah，blah，blah，]，[blah，blah，blah]，[blah，blah，blah]]，[[blah，blah，blah，]，[blah，blah，blah]，[等等，等等，等等]，[[等等，等等，]，[等等，等等，]]]

所有即时消息都是： [[[[blah，blah，blah，]，[blah，blah，blah]，[blah，blah，blah]]，[[]]，[[]]]

Answer 1

遍历csv.reader的行时，您正在浏览整个文件，而不会后退。不幸的是，您无法使用csv.reader通过使用两个遍历整个文件的单独的for循环来两次读取同一打开的文件。

要两次遍历csv.reader的行，您需要将这些行存储在这样的单独变量中：

wA = csv.reader("warehouse_A")
wA_list = list(wA)

for row in wA_list:
    a_itemno.append(row[0])
for row in wA_list:
    a_value.append(row[2])

或者，如果您的文件太大而无法加载到内存中，请考虑修改逻辑并一次完成所需的所有操作，例如：

for row in wA:
    a_itemno.append(row[0])
    a.descripton.append(row[1])
    a_value.append(row[2])

包含3个数组的数组只会打印一个（python）

1 个答案: