'AttributeError' when adding elements to a Python list

Question

I am newer to python and I am having trouble saving a list of renamed files so I can eventually move the files to a new directory. My code is posted below:

import os
new_files = []

        for orig_name in orig:           #This loop splits each file name into a list of stings containing each word
            if '.' in orig_name:            #This makes sure folder names are not changed, only file names
                base = os.path.splitext(orig_name)[0]
                ext = os.path.splitext(orig_name)[1]
                sep = base.split()             #Separation is done by a space
                for t in sep:           #Loops across each list of strings into an if statement that saves each part to a specific variable
                    if t.isalpha() and len(t) == 3:
                        wc = t
                        wc = wc.upper()
                    elif len(t) > 3 and len(t) < 6:
                        wc = t
                        wc = wc.upper()
                    elif len(t) >= 4:
                        pnum = t
                        if pnum.isalnum:
                            pnum = pnum.upper()
                    elif t.isdecimal() and len(t) < 4:
                        opn = t
                        if len(opn) == 2:
                            opn = '0' + opn
                    else:
                        pass
                new_nam = '%s OP %s %s' % (pnum, opn, wc)          #This is the variable that contain the text for the new name
                new_nam = new_nam + ext
                new_files = new_files.append(new_nam)
                print(new_files)

Basically what this code does is loops over the original file names (orig), and renames them to a specific convention (new_name). The issue I am having is for every iteration, I am trying to save each new_nam to the list "new_files" however I keep getting this error:

line 83, in <module>
    new_files = new_files.append(new_nam)
AttributeError: 'NoneType' object has no attribute 'append'

Basically I think it is saying you cannot add a "None Type" to a list which makes sense, however when I print all of the new_nam's, they are all string which is not a None type. So I guess I don't know why this code isn't adding each new file name to the new_files list. Any advice of tips is greatly appreciated, cannot figure this one out :/ Thanks!

cs95 · Accepted Answer · 2017-08-14 02:46:16Z

2

list.append is an inplace operation. You must call the function without assigning the return value:

In [122]: data = [1, 2, 3]

In [123]: data.append(12345)

In [124]: data
Out[124]: [1, 2, 3, 12345]

In your case, you'll need

new_files.append(new_nam)

All the list.___ methods as described in the list docs are inplace.

answered Aug 14, 2017 at 2:46

cs95

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1 Comment

Bkal05 Over a year ago

Oh wow I knew it was something silly, well thank you for that, learning something new every day!!

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