plot_bars.py

import matplotlib.pyplot as plt

def plot_bars(barGroups, barNames, groupNames, colors, ylabel="", title="", width=0.8):
    """Plot a grouped bar chart
    barGroups  - list of groups, where each group is a list of bar heights
    barNames   - list containing the name of each bar within any group
    groupNames - list containing the name of each group
    colors     - list containing the color for each bar within a group
    ylabel     - label for the y-axis
    title      - title
    """
    fig, ax = plt.subplots()
    offset = lambda items, off: [x + off for x in items]

    maxlen = max(len(group) for group in barGroups)
    xvals = range(len(barGroups))
    
    for i, bars in enumerate(zip(*barGroups)):
        print(bars)
        plt.bar(offset(xvals, i * width/maxlen), bars, width/maxlen, color=colors[i])

    ax.set_ylabel(ylabel)
    ax.set_title(title)
    ax.set_xticks(offset(xvals, width / 2))
    ax.set_xticklabels(groupNames)

    # Shrink current axis by 20%
    box = ax.get_position()
    ax.set_position([box.x0, box.y0, box.width * 0.8, box.height])

    # Put a legend to the right of the current axis
    ax.legend(barNames, loc="upper left", bbox_to_anchor=(1, 1))