title: PermissionError: [Errno 13] Permission denied: 'pro.csv'
body: <blockquote>
    <p>I want to change the null values in the dataset to "not mentioned" but
    unable to do so. I am new to this so if any naive error , I apologize.
    Please help.</p>
  </blockquote>
  
  <pre><code>Name: website, Length: 2407, dtype: object
  Traceback (most recent call last):
    File "project1.py", line 19, in &lt;module&gt;
      df.to_csv("pro.csv", index=False)
    File "C:\Users\Lucifer Morningstar\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pandas\core\generic.py", line 3228, in to_csv
      formatter.save()
    File "C:\Users\Lucifer Morningstar\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pandas\io\formats\csvs.py", line 183, in save
      compression=self.compression,
    File "C:\Users\Lucifer Morningstar\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pandas\io\common.py", line 399, in _get_handle
      f = open(path_or_buf, mode, encoding=encoding, newline="")
  PermissionError: [Errno 13] Permission denied: 'pro.csv'
  </code></pre>
  
  <p>My program code is :-</p>
  
  <pre><code>#Data Cleaning with Python Pandas
  #Missing Values
  
  import pandas as pd
  import numpy as np
  
  #Standard Missing Values
  df = pd.read_csv("breweries_us.csv")
  a=df["website"]
  b=df["website"].isnull()
  print(a)
  print(b)
  
  #replacing missing values
  c=df["website"]
  df["website"].fillna("not mentioned",inplace=True)
  d=df["website"]
  print(d)
  df.to_csv("pro.csv", index=False)
  </code></pre>