TypeError: can only concatenate list (not "str") to list when upload to aws s3 bucket using boto3

I am trying to create a script that will place a file inside a folder in the s3 bucket. Here’s my code:

AccountName = ["AWSAccountName"]

def upload_s3(AccountName,bucket,filename):
    dir = os.getcwd()
    s3 = boto3.client('s3')
    #prefix = 'folder_' + datetime.now().strftime("%Y-%m-%d_%H-%M-%S") + "/" + filename
    prefix =  AccountName + 'folder_' + datetime.now().strftime("%Y-%m-%d_%H-%M-%S") + "/" + filename
    #s3object = s3.put_object(Bucket=bucket, Key=prefix)
    s3.upload_file(dir + '/' +filename, bucket, prefix)

if __name__ == "__main__":
    upload_s3(AccountName, "ec2-idle-workspace-list","EC2_Idle_info_cpu_NetworkIn_NetworkOut.csv")

However, while running the script, it gives me the following error:

 prefix =  AccountName + 'folder_' + datetime.now().strftime("%Y-%m-%d_%H-%M-%S") + "/" + filename
TypeError: can only concatenate list (not "str") to list
[Pipeline] echo
script returned exit code 1

>Solution :

You are trying to concatenate AccountName + 'folder_' + datetime.now().strftime("%Y-%m-%d_%H-%M-%S") + "/" + filename but AccountName is a list, not a string.

Replace AccountName = ["AWSAccountName"] with AccountName = "AWSAccountName".

Or replace
AccountName + 'folder_' + datetime.now().strftime("%Y-%m-%d_%H-%M-%S") + "/" + filename
With
AccountName[0] + 'folder_' + datetime.now().strftime("%Y-%m-%d_%H-%M-%S") + "/" + filename