Python：遍历嵌套字典时的冗余

Question

I have a nested dictionary which I am trying to loop through in order to write to an excel file.

This is the code which initiates and creates the nested dictionary

def tree(): return defaultdict(tree)
KMstruct = tree()
for system in sheet.columns[0]:
if system.value not in KMstruct:
    KMstruct[system.value]
    for row in range(1,sheet.get_highest_row()+1):
        if sheet['A'+str(row)].value == system.value and sheet['B'+str(row)].value not in KMstruct:
            KMstruct[system.value][sheet['B'+str(row)].value]
            if sheet['B'+str(row)].value == sheet['B'+str(row)].value and sheet['C'+str(row)].value not in KMstruct:
                KMstruct[system.value][sheet['B'+str(row)].value][sheet['C'+str(row)].value]
                if sheet['C'+str(row)].value == sheet['C'+str(row)].value and sheet['D'+str(row)].value not in KMstruct:
                    KMstruct[system.value][sheet['B'+str(row)].value][sheet['C'+str(row)].value][sheet['D'+str(row)].value]
                    KMstruct[system.value][sheet['B'+str(row)].value][sheet['C'+str(row)].value][sheet['D'+str(row)].value] = [sheet['E'+str(row)].value]

This is the code where I loop through it:

for key in KMstruct.keys():
r += 1
worksheet.write(r, col,     key)
for subkey in KMstruct[key]:
    if currsubkeyval != subkey:
        r += 1
        worksheet.write(r, col,     key)
    r +=1
    worksheet.write(r, col, key + '\\' + subkey)
    for item in KMstruct[key][subkey]:
        if curritemval != item:
            r +=1
            worksheet.write(r, col, key + '\\' + subkey)
        for subitem in KMstruct[key][subkey][item]:
            r += 1
            worksheet.write(r, col, key + '\\' + subkey + '\\' + item)
            worksheet.write(r, col + 1, subitem)
            curritemval = item
            for finalitem in KMstruct[key][subkey][item][subitem]:
                r += 1
                worksheet.write(r, col, key + '\\' + subkey + '\\' + item + '\\' + subitem)
                worksheet.write(r, col + 1, KMstruct[key][subkey][item][subitem])

Bear with me on this code since I am a noob, I am aware that this is not so beautiful. Anyhow, my problem is the last loop. I am trying to take the string values in KMstruct[key][subkey][item][subitem] but the loop variable lastitem goes through each char of key's string value (note: the key subitem contains a list of strings). This means that if I only have one value that is to be written, it gets written as many times as there are characters in the string.

Eg: value: apple will be written on a new excel row 5 times

What am I doing wrong here?

Edit: The issue on the redundancy has been solved but now I need to understand if I am doing something wrong when assigning my lastitem, ie my list of strings, to the subitem key.

Answer 1

Your immediate problem is that the last line of your example should be:

                worksheet.write(r,col+1, finalitem)

BTW, your code would be a lot easier to read if you created occasional temporary variables like:

        subitemlist = KMstruct[key][subkey][item]
        for subitem in subitemlist:

Answer 2

The problem is that in Python a str is also an iterable, for example:

>>> for s in 'hello':
...    print(s)

h
e
l
l
o

So you either need to avoid iterating when the value is a str , or wrap the str in another iterable (eg a list ) so that it can be handled the same way. This is made slightly difficult by how you are structuring your code. For example, the following:

for key in KMstruct.keys():
    for subkey in KMstruct[key]:

...can be written as:

for key, value in KMstruct.items():
    for subkey, subvalue in value.items():

...giving you the value on each loop, making it possible to apply a test.

for key, val in KMstruct.items():
r += 1
worksheet.write(r, col,     key)

for subkey, subval in val.items():
    if currsubkeyval != subkey:
        r += 1
        worksheet.write(r, col,     key)
    r +=1
    worksheet.write(r, col, key + '\\' + subkey)

    for item, itemval in subval.items():
        if curritemval != item:
            r +=1
            worksheet.write(r, col, key + '\\' + subkey)

        for subitem, subitemval in itemval.items():
            r += 1
            worksheet.write(r, col, key + '\\' + subkey + '\\' + item)
            worksheet.write(r, col + 1, subitem)
            curritemval = item

            # I am assuming at this point subitemval is either a list or a str?
            if type(subitemval) == str:
                # If it is, wrap it as a list, so the next block works as expected
                subitemval = [subitemval] 

            for finalitem in subitemval:
                r += 1
                worksheet.write(r, col, key + '\\' + subkey + '\\' + item + '\\' + subitem)
                worksheet.write(r, col + 1, finalitem) # This should be finalitem, correct?

Here we test the type of the subitemval and if it is a str wrap it in a list [str] so the following block iterates as expected. There is also an apparent bug where you are not outputting the finalitem on the last line. It's not posssible to test this without your example data but it should be functionally equivalent.