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python - How to handle a KeyError when working with a list inside a list

问题描述

I have written two functions in Python that I intend to re-use multiple times. Together they will allow me to calculate the total travel distance of a vehicle in a warehouse collecting goods from defined locations in a single aisle.

One function get_orderpick extracts two lists from input data in a dataFrame and returns them in a list, so the return clause looks like this: return [orderList, pickList].

When I run this function alone I appear to get a list with two lists stored inside it, no problem. BUT when I attempt to feed this through to my next function I get a KeyError.

So as I mentioned, the first function get_orderpick appears to work just fine, here's the full code:

def get_orderpick(df):
    # Produce a standard Python list of the picks
    # DataFrame -> numpy.array -> list

    pickList = df.sku.values.tolist()
    orderList = df.order.values.tolist()

    return [orderList, pickList]

Note - orderList is the sequence of picks, I need to track when the vehicle must return to base and start over again on the next order. It contains only numbers; pickList is the bay from which the pick must take place, this determines how far the vehicle must travel for each pick and contains a single capital letter in each entry.

Here is the distance calculation function:

def picking_distance(lists, layout):

    orderList = lists[1] #<------------------ issue here
    pickList = lists[2] 

    totalDistance = 0 # distance
    currentPos = 0  # position
    for i in range(len(pickList)):
        if orderList[i] == 1 and currentPos != 0:
            # new order, return to base
            totalDistance += currentPos
            currentPos = 0
            i -= 1 # begin the pick from base again
        else:
            nextPos = layout[pickList[i]]
            delta = abs(nextPos - currentPos)
            totalDistance += delta
            currentPos = nextPos
    return totalDistance

I would expect the code to produce the total distance traveled. But I get a KeyError when I try to separate out the orderList and pickList from the lists list. I am calling the functions together in the following way:

print(picking_distance(layout, get_orderpick(data)))

Thanks for your help!

P.S. I pass through a dictionary called layout on the second function. This determines the distance between picking locations.

标签： pythonpython-3.xlistdataframe

解决方案

所以......我犯了一个错误，在调用我自己的函数时改变了我的论点。

这意味着我正在传递一个字典，该函数需要一个列表列表。

切换参数已经解决了这个问题，而且效果很好。

print(picking_distance(get_orderpick(data), layout))

故事的道德启示

如果在您希望处理列表时遇到字典错误……您可能以错误的顺序传递参数。

谢谢你的时间！:D

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