How to count all values of a one column?

Question

I am trying to count all the instances of all values of col_a

for example:

col_a

 A

 B

 C

 A

 D

 B

 A

Is there one line of code I can use that would tell me how many times each value (A,B,C,D) exist in that column?

Answer 1

So, the solution for this can be value_counts

df.col_a.value_counts()

Or, you can use groupby with size:

>>> df.groupby('col_a').size()

col_a

A    3

B    2

C    1

D    1

dtype: int64

>>>