count values of rows by columns pandas code example
Example 1: pandas count rows with value
len(df[df['score'] == 1.0])
Example 2: pandas get count of column
df['column_name'].value_counts()
Example 3: pandas count values by column
df = pd.DataFrame({'a':list('abssbab')})
df.groupby('a').count()
Example 4: python count variable and put the count in a column of data frame
df['freq'] = df.groupby('myvar')['myvar'].transform('count')