Count the frequency that a value occurs in a dataframe column


I have a dataset

cat a
cat b
cat a

I’d like to be able to return something like (showing unique values and frequency)

category   freq 
cat a       2
cat b       1
Asked By: yoshiserry



Use value_counts() as @DSM commented.

In [37]:
df = pd.DataFrame({'a':list('abssbab')})


b    3
a    2
s    2
dtype: int64

Also groupby and count. Many ways to skin a cat here.

In [38]:


a  2
b  3
s  2

[3 rows x 1 columns]

See the online docs.

If you wanted to add frequency back to the original dataframe use transform to return an aligned index:

In [41]:
df['freq'] = df.groupby('a')['a'].transform('count')


   a freq
0  a    2
1  b    3
2  s    2
3  s    2
4  b    3
5  a    2
6  b    3

[7 rows x 2 columns]
Answered By: EdChum

Using list comprehension and value_counts for multiple columns in a df

[my_series[c].value_counts() for c in list(my_series.select_dtypes(include=['O']).columns)]

Answered By: Shankar ARUL

If you want to apply to all columns you can use:


This will apply a column based aggregation function (in this case value_counts) to each of the columns.

Answered By: Arran Cudbard-Bell

In 0.18.1 groupby together with count does not give the frequency of unique values:

>>> df
0  a
1  b
2  s
3  s
4  b
5  a
6  b

>>> df.groupby('a').count()
Empty DataFrame
Columns: []
Index: [a, b, s]

However, the unique values and their frequencies are easily determined using size:

>>> df.groupby('a').size()
a    2
b    3
s    2

With df.a.value_counts() sorted values (in descending order, i.e. largest value first) are returned by default.

Answered By: Vidhya G

Without any libraries, you could do this instead:

def to_frequency_table(data):
    frequencytable = {}
    for key in data:
        if key in frequencytable:
            frequencytable[key] += 1
            frequencytable[key] = 1
    return frequencytable


>>> {1: 4, 2: 1, 3: 1, 4: 2}
Answered By: Timz95

value_counts – Returns object containing counts of unique values

apply – count frequency in every column. If you set axis=1, you get frequency in every row

fillna(0) – make output more fancy. Changed NaN to 0

Answered By: Roman Kazakov

If your DataFrame has values with the same type, you can also set return_counts=True in numpy.unique().

index, counts = np.unique(df.values,return_counts=True)

np.bincount() could be faster if your values are integers.

Answered By: user666

This short little line of code will give you the output you want.

If your column name has spaces you can use

Answered By: Satyajit Dhawale

You can also do this with pandas by broadcasting your columns as categories first, e.g. dtype="category" e.g.

cats = ['client', 'hotel', 'currency', 'ota', 'user_country']

df[cats] = df[cats].astype('category')

and then calling describe:


This will give you a nice table of value counts and a bit more :):

    client  hotel   currency    ota user_country
count   852845  852845  852845  852845  852845
unique  2554    17477   132 14  219
top 2198    13202   USD Hades   US
freq    102562  8847    516500  242734  340992
Answered By: tsando
n_values = data.income.value_counts()

First unique value count

n_at_most_50k = n_values[0]

Second unique value count

n_greater_50k = n_values[1]



<=50K    34014
>50K     11208

Name: income, dtype: int64


(11208, 34014)
Answered By: RAHUL KUMAR

@metatoaster has already pointed this out.
Go for Counter. It’s blazing fast.

import pandas as pd
from collections import Counter
import timeit
import numpy as np

df = pd.DataFrame(np.random.randint(1, 10000, (100, 2)), columns=["NumA", "NumB"])


%timeit -n 10000 df['NumA'].value_counts()
# 10000 loops, best of 3: 715 µs per loop

%timeit -n 10000 df['NumA'].value_counts().to_dict()
# 10000 loops, best of 3: 796 µs per loop

%timeit -n 10000 Counter(df['NumA'])
# 10000 loops, best of 3: 74 µs per loop

%timeit -n 10000 df.groupby(['NumA']).count()
# 10000 loops, best of 3: 1.29 ms per loop


Answered By: dragonfire_007
your data:

cat a
cat b
cat a


 df['freq'] = df.groupby('category')['category'].transform('count')
 df =  df.drop_duplicates()
Answered By: Rahul Jain

I believe this should work fine for any DataFrame columns list.

def column_list(x):
    column_list_df = []
    for col_name in x.columns:
        y = col_name, len(x[col_name].unique())
return pd.DataFrame(column_list_df)

column_list_df.rename(columns={0: "Feature", 1: "Value_count"})

The function “column_list” checks the columns names and then checks the uniqueness of each column values.

Answered By: djoguns

The following code creates frequency table for the various values in a column called "Total_score" in a dataframe called "smaller_dat1", and then returns the number of times the value "300" appears in the column.

valuec = smaller_dat1.Total_score.value_counts()
Answered By: EArwa

As everyone said, the faster solution is to do:


But if you want to use the output in your dataframe, with this schema:

df input:

cat a
cat b
cat a

df output: 

category   counts
cat a        2
cat b        1 
cat a        2

you can do this:

df['counts'] =
Answered By: L F
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