Pandas: Filter rows depending on number of occurrences of target string

Given this sample data:

I only want to keep rows in column temp that has only one period, so the above data would become:

Is there a way to do this with a lambda function, preferably?

>Solution :

You can try this:

df.loc[df['temp'].str.count(r'\.').eq(1)]

   temp
0  a. b
3  ab.c