TypeError: cannot convert datetimelike to dtype [datetime64[s]]
#### 1ST ISSUE
#### This is part of the function that generates the warning 

``` 
    data = urllib.request.urlopen(dataLink)
    data = data.read().decode("utf-8")
    data = json.loads(data)
    
    data = data["btc_usd"]
    data = pd.DataFrame(data)
    
    buys = data[(data['type']=="bid")]
    buys["datestamp"] = np.array(buys["timestamp"]).astype("datetime64[s]")
    buyDates = (buys["datestamp"]).tolist()
    
    sells = data[(data['type']=="ask")]
    sells["datestamp"] = np.array(sells["timestamp"]).astype("datetime64[s]")
    sellDates = (sells["datestamp"]).tolist()
    
    a.clear()
    a.plot_date(buyDates, buys["price"])
    a.plot_date(sellDates, sells["price"])
```
#### Problem description - It throws me this warning

```
__main__:36: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy
__main__:41: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy
```



-----------------------------------------------------------------------------------------------------------------
#### 2ND ISSUE
#### As far as I understand, all I had to do is to use .loc this way:
``` 
    buys = data[(data['type']=="bid")]
    buys.loc[:, "datestamp"] = np.array(buys["timestamp"]).astype("datetime64[s]")
    buyDates = (buys["datestamp"]).tolist()
    

    sells = data[(data['type']=="ask")]
    sells.loc[:, "datestamp"] = np.array(sells["timestamp"]).astype("datetime64[s]")
    sellDates = (sells["datestamp"]).tolist()
```
However, if I run that I get this error:

```
Traceback (most recent call last):
  File "C:\Users\amoro\Anaconda3\lib\site-packages\matplotlib\cbook\__init__.py", line 388, in process
    proxy(*args, **kwargs)
  File "C:\Users\amoro\Anaconda3\lib\site-packages\matplotlib\cbook\__init__.py", line 228, in __call__
    return mtd(*args, **kwargs)
  File "C:\Users\amoro\Anaconda3\lib\site-packages\matplotlib\animation.py", line 1081, in _start
    self._init_draw()
  File "C:\Users\amoro\Anaconda3\lib\site-packages\matplotlib\animation.py", line 1792, in _init_draw
    self._draw_frame(next(self.new_frame_seq()))
  File "C:\Users\amoro\Anaconda3\lib\site-packages\matplotlib\animation.py", line 1814, in _draw_frame
    self._drawn_artists = self._func(framedata, *self._args)
  File "<ipython-input-2-71112d20e664>", line 36, in animate
    buys.loc[:, "datestamp"] = np.array(buys["timestamp"]).astype("datetime64[s]")
  File "C:\Users\amoro\Anaconda3\lib\site-packages\pandas\core\indexing.py", line 189, in __setitem__
    self._setitem_with_indexer(indexer, value)
  File "C:\Users\amoro\Anaconda3\lib\site-packages\pandas\core\indexing.py", line 362, in _setitem_with_indexer
    self.obj[key] = _infer_fill_value(value)
  File "C:\Users\amoro\Anaconda3\lib\site-packages\pandas\core\frame.py", line 3119, in __setitem__
    self._set_item(key, value)
  File "C:\Users\amoro\Anaconda3\lib\site-packages\pandas\core\frame.py", line 3194, in _set_item
    value = self._sanitize_column(key, value)
  File "C:\Users\amoro\Anaconda3\lib\site-packages\pandas\core\frame.py", line 3411, in _sanitize_column
    value = maybe_cast_to_datetime(value, value.dtype)
  File "C:\Users\amoro\Anaconda3\lib\site-packages\pandas\core\dtypes\cast.py", line 1001, in maybe_cast_to_datetime
    "dtype [{dtype}]".format(dtype=dtype))
TypeError: cannot convert datetimelike to dtype [datetime64[s]]
```
Up to this point I am completely lost and I would really apreciate If anyone could answer this post with the code above modified, so that the warning and the error don´t appear anymore.

Also if I did something wrong when using .loc PLEASE let me now so that I can change it and avoid any errors 

Note: I am using Python 3.5, and I can´t upgrade it nor downgrade it for various reasons, and this is part of a tutorial in Python 3.4 