binning_with_dicts.py

from bisect import bisect_left
import pandas as pd

# Create Example Fixture
data = [['A', 1], ['B', 3], ['C', 5]]
df = pd.DataFrame(data=data, columns=('ID', 'Delta'))

## Example 1
# Build out a very large dict with a discrete value key for every
# possible value in the bin.  Works with ints

# Create High level bin map
bin_generator = {'(0, 3)': {'low': 0, 'high': 3},
                 '(3, 4)': {'low': 3, 'high': 4},
                 '(4, 7)': {'low': 4, 'high': 7}}

# Function to generate a 'long' map from the high level 
def generate_bin_map(bin_gen):
    bin_map = dict()
    for key in bin_gen.keys():
        for value in range(bin_gen.get(key).get('low'), bin_gen.get(key).get('high')):
            bin_map[value] = key
    return bin_map

# Create Mapping Dict
bin_map = generate_bin_map(bin_generator)

df['bin'] = df.Delta.map(bin_map)
df


## Example 2
# Build out a small dict using the category and the lower bound of each bin
# Works with floats or continuous keys.

# Generates a { lowerbound_value: bin } dict from bin_generator
def generate_bin_map_2(bin_gen):
    bin_map = dict()
    for key in bin_gen.keys():
        bin_map[bin_gen.get(key).get('low')] = key
    return bin_map
    
bin_map_2 = generate_bin_map_2(bin_generator)

# Finds the relative position of the value within the list of keys then
# returns the bin for the key to the left.
def apply_bin_map(x, bin_map):
    key_list = list(bin_map.keys())
    if x in key_list:
        tier = key_list[bisect_left(key_list, x)]
    else:
        tier = key_list[bisect_left(key_list, x)-1] 
    return bin_map.get(tier)
    
df['bin_2'] = df.Delta.apply(lambda x: apply_bin_map(x, bin_map_2))
df