如何使用Python在底图中添加图例

我正在尝试在世界地图上添加一个图例。每一点都是来自不同推文的不同类型的设备。

这是我的代码：

import geocoder
import json
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

def openJSON(file, path):
    with open(path + file + '.json', 'r') as fp:
        data = json.load(fp)
        return data


def App_users(data):
    android_users = []
    iphone_users = []
    other_users = []

    #3 types of users: Android, Iphone and others:
    for a, b, c, d in data:
        if "Twitter for Android" in d:
            android_users.append([a, b])
        elif "Twitter for iPhone" in d:
            iphone_users.append([a, b])
        else:
            other_users.append([a, b])

    data = (android_users, iphone_users, other_users)
    return data


if __name__ == '__main__':

    posXY_add = []

    for d in data[0:50]:
        if d["user"]["location"] != None:
            g = geocoder.google(d["user"]["location"])
            if g.latlng != None:
                a = g.latlng + [g.address] + [str(d["source"])]
                posXY_add.append(a)

    data = App_users(posXY_add)

    map = Basemap(llcrnrlat=-70, urcrnrlat=70,
                    llcrnrlon=-180, urcrnrlon=180, epsg=3395)
    map.arcgisimage(service='ESRI_Imagery_World_2D', xpixels = 1500, verbose= True)

    colors = ['r', 'g', 'b']
    increment = 0

    for app in data:
        for item in app:
            if len(item) == 2:
                lat, lon = item[0], item[1]
                x, y = map(lon, lat)
                map.plot(x, y, colors[increment] + 'o')
        increment += 1


    plt.title("Geo-position Twitter Devices")
    plt.show()

您有什么建议来改善我的地图吗？不同的颜色，不同的地图？我正在使用Pycharm的Python 2.7。我的样本数据是：

([[21.8974003, 83.39496319999999], [40.2671941, -86.1349019], [10.4805937, -66.90360629999999]], [[50.719164, -1.880769], [37.0903748, -94.5134078], [44.9862701, -93.39398279999999], [47.6062095, -122.3320708], [-27.4697707, 153.0251235], [20.593684, 78.96288]], [[43.2648545, -79.9492978], [39.1767262, -94.4867155], [33.7489954, -84.3879824], [39.7392358, -104.990251], [38.8761634, -77.0337777], [41.0082376, 28.9783589], [36.0753128, -95.95646269999999], [36.0595387, -95.90582429999999], [29.7604267, -95.3698028], [21.3014947, 106.6291304], [21.3014947, 106.6291304], [-16.6868982, -49.2648114], [10.4805937, -66.90360629999999], [45.037149, -92.825929], [33.760818, -78.967556], [45.49340369999999, -73.82329179999999], [39.750545, 37.0150217]])