Counting unique values in a column in pandas dataframe like in Qlik?

Question

Count distinct values, use nunique:

df['hID'].nunique()
5

Count only non-null values, use count:

df['hID'].count()
8

Count total values including null values, use the size attribute:

df['hID'].size
8

Edit to add condition

Use boolean indexing:

df.loc[df['mID']=='A','hID'].agg(['nunique','count','size'])

OR using query:

df.query('mID == "A"')['hID'].agg(['nunique','count','size'])

Output:

nunique    5
count      5
size       5
Name: hID, dtype: int64

If I assume data is the name of your dataframe, you can do :

data['race'].value_counts()

this will show you the distinct element and their number of occurence.

Or get the number of unique values for each column:

df.nunique()

dID    3
hID    5
mID    3
uID    5
dtype: int64

---

New in pandas 0.20.0 pd.DataFrame.agg

df.agg(['count', 'size', 'nunique'])

         dID  hID  mID  uID
count      8    8    8    8
size       8    8    8    8
nunique    3    5    3    5

---

You've always been able to do an agg within a groupby. I used stack at the end because I like the presentation better.

df.groupby('mID').agg(['count', 'size', 'nunique']).stack()


             dID  hID  uID
mID                       
A   count      5    5    5
    size       5    5    5
    nunique    3    5    5
B   count      2    2    2
    size       2    2    2
    nunique    2    2    2
C   count      1    1    1
    size       1    1    1
    nunique    1    1    1

You can use nunique in pandas:

df.hID.nunique()
# 5

To count unique values in column, say hID of dataframe df, use:

len(df.hID.unique())

I was looking for something similar and I found another way you may help you

• If you want to count the number of null values, you could use this function:

def count_nulls(s):
    return s.size - s.count()

• If you want to include NaN values in your unique counts, you need to pass dropna=False to the nunique function.

def unique_nan(s):
    return s.nunique(dropna=False)

• Here is a summary of all the values together using the titanic dataset:

from scipy.stats import mode

agg_func_custom_count = {
    'embark_town': ['count', 'nunique', 'size', unique_nan, count_nulls, set]
}
df.groupby(['deck']).agg(agg_func_custom_count)

You can find more info Here