title: FileNotFoundError: [Errno 2] No such file or directory: '9788427133310_urls.csv'
body: <p>I'm trying to take all files in a folder, join them and put their names in their rows so I can distinguish them. However, I get:</p>
  <pre><code>Traceback (most recent call last):
    File &quot;C:/unite_try.py&quot;, line 21, in &lt;module&gt;
      with open(file, newline='') as f:
  FileNotFoundError: [Errno 2] No such file or directory: '9788427133310_urls.csv'
  </code></pre>
  <p>The file, which is the first one in the folder, is in the right folder so I don't understand why this is happening. When I print &quot;files&quot; they are correct.</p>
  <pre><code>folder = './urls_files'
  files = []
  for file in os.listdir(folder):
      if file.endswith('.csv'):
          files.append(file)
  with open('./urls_files/results.csv', 'w', newline='') as fw:
      cw = csv.writer(fw, delimiter=',')
      for file in files:
          with open(file, newline='') as f:
              for row in csv.reader(f, delimiter=','):
                  row.append(file)
                  cw.writerow(row)
  </code></pre>