How to continuously count the number of times the column value=0 and restart when value>0-CodePudding

I want to go from this:

to this:

    df
     val1    count                  
0     0       1
1     0       2
2     32      0
3     0       1

How do I count how many times 0 comes in a row?

CodePudding user response：

Make groups df.val1.ne(0).cumsum(), this makes a new group every time val1 isn't 0.
Groupby those groups, and cumsum() where the number equals 0 in each group.

df['count'] = df.groupby(df.val1.ne(0).cumsum())['val1'].apply(lambda x: x.eq(0).cumsum())
print(df)

# Output:
   val1  count
0     0      1
1     0      2
2    32      0
3     0      1

CodePudding user response：

You can use groupby.cumcount using the non-0 values to restart the groups, then mask:

m = df['val1'].ne(0)
df['count'] = df.groupby(m.cumsum()).cumcount().add(1).mask(m, 0)

Output:

   val1  count
0     0      1
1     0      2
2    32      0
3     0      2