Python Script Error: TypeError: can only concatenate str (not "list") to str

Question

Currently I am trying to write a script that will look inside a bunch of csv files in a folder and find a specific column, see if there is a specific value, and then replace that value with the new one in all of these files. Currently receiving this error: "TypeError: can only concatenate str (not "list") to str". Do I need to add them all to one dataframe first and then try it again? I thought that was what I was doing. Any help would be appreciated. Thanks!

Traceback (most recent call last):
  File "Rename_Tool.py", line 55, in <module>
    worker(files)
  File "Rename_Tool.py", line 38, in worker
    with open(dest_dir + filenames) as f:
TypeError: can only concatenate str (not "list") to str



src_dir = 'H:\\PCoE\\Users\\VanBecelaere_C\\Data Initiative Project\\Tables'
dest_dir = 'H:\\PCoE\\Users\\VanBecelaere_C\\Data Initiative Project\\Updated Tables'
 

file_count = 0
start_time = time.time()

def worker(files):

    filenames = [file + '.csv' for file in files]
    for filename in filenames:              
        # read header
        with open(dest_dir + filenames) as f:
            read_data = f.read()
        header = read_data[:read_data.find('!1')]
        idx = header.find('\n')

        # read data
        df1 = pd.read_csv(dest_dir + filename, skiprows=4, encoding='ISO-8859-1', nrows=1) # read column header only - to get the list of columns
        dtypes = {}
        for col in df1.columns:# make all columns text, to avoid formatting errors
            dtypes[col] = 'str'
        df1 = pd.read_csv(dest_dir + filename, dtype=dtypes, skiprows=4, encoding='ISO-8859-1', quotechar="'")
        
        # drop footer
        df1 = df1.loc[df1['!']=='*']

        df1.loc[df['PROD_NAME'].str.contains('NA_NRF'), 'PROD_NAME_NAME'] = 'FA_GUAR'
        file_count += 1 # count the fil
worker(files)

"Okay it was updated " Okay, now look at the message carefully. Notice how it highlights the line of code, with open(dest_dir + filenames) as f? That's the part where you want to concatenate, right? The dest_dir + filenames part? So - does filenames make sense there? (Hint: what is the type of dest_dir? What is the type of filenames? Do you see how that relates to the error message?) Finally: where the code says for filename in filenames:, does that give a hint as to how to fix the problem? — Karl Knechtel
– Karl Knechtel, Commented Aug 18, 2022 at 1:17

itogaston · Accepted Answer · 2022-08-18 01:22:27Z

0

with open(dest_dir + filenames) as f:

The error says that you can not add a list to a string. filenames is the list:

filenames = [file + '.csv' for file in files]

So probably you wanted something like:

for filename in filenames:              
        # read header
        with open(dest_dir + filename) as f:

Note that filename is an element of the list filenames

answered Aug 18, 2022 at 1:22

itogaston

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