Python Pandas: Calculate moving average within group : <p>I have a dataframe containing time series for 100 objects:</p>

<pre><code>object  period  value 
1       1       24
1       2       67
...
1       1000    56
2       1       59
2       2       46
...
2       1000    64
3       1       54
...
100     1       451
100     2       153
...
100     1000    21
</code></pre>

<p>I want to calculate moving average with window 10 for the <code>value</code> column. I guess I have to do something like</p>

<pre><code>df.groupby('object').apply(lambda ~calculate MA~) 
</code></pre>

<p>and then merge this Series to the original dataframe by object? Can't figure out exact commands</p>
