Python3 数据可视化之matplotlib、Pygal、requests

matplotlib的学习和使用

matplotlib的安装

pip3 install matplotlib

简单的折线图

import  matplotlib.pyplot as plt
#绘制简单的图表 input_values = [1,2,3,4,5] squares = [1,4,9,16,25] plt.plot(input_values,squares,linewidth=5) #设置图表的标题 并给坐标轴加上标签 plt.title("Square Number",fontsize=24) plt.xlabel("Value",fontsize=24) plt.ylabel("Square of Value",fontsize=14) #设置刻度标记的大小 plt.tick_params(axis='both',labelsize=14) #显示图表 plt.show() #保存在当前的目录下，文件名为squares_plot.png #plt.savefig('squares_plot.png', bbox_inches='tight')

绘制简单的散点图

import matplotlib.pyplot as plt x_values = [1, 2, 3, 4, 5] y_values = [1, 4, 9, 16, 25] plt.scatter(x_values, y_values, s=100) #设置图表的标题 并给坐标轴加上标签 plt.title("Square Number",fontsize=24) plt.xlabel("Value",fontsize=24) plt.ylabel("Square of Value",fontsize=14) #设置刻度标记的大小 plt.tick_params(axis='both',labelsize=14) plt.show()

import  matplotlib.pyplot as plt

#绘制散点图并设置其样式 x_value = list(range(1,1001)) y_value = [x**2 for x in x_value] #点的颜色 c=(0,0,1,0.5) edgecolors = 'red' 点的边缘颜色 plt.scatter(x_value,y_value,c=y_value,cmap=plt.cm.Blues,edgecolors='none',s=40) # plt.scatter(2,4,s=200) #设置图表的标题 并给坐标轴加上标签 plt.title("Square Number",fontsize=24) plt.xlabel("Value",fontsize=24) plt.ylabel("Square of Value",fontsize=14) #设置刻度标记的大小 plt.tick_params(axis='both',labelsize=14) #设置每个坐标系的取值范围 # plt.axis([0,110,0,110000]) #显示 plt.show() #显示并保存 #plt.savefig('pyplot_scatter.png',bbox_inches='tight')

绘制随机漫步图

random_walk.py

from random import choice class RandomWalk(): """一个生成随机漫步数据的类""" def __init__(self,num_points=5000): """一个生成随机漫步的数据的类""" self.num_points = num_points; #所有的随机漫步都始于（0，0） self.x_value = [0] self.y_value = [0] def fill_walk(self): """计算随机漫步包含的点""" #不断漫步，直到列表达到指定的长度 while len(self.x_value) < self.num_points: #决定前进的方向以及沿这个方向前进的距离 x_direction= choice([1,-1]) x_distance = choice([0,1,2,3,4]) x_step = x_direction*x_distance y_direction = choice([1,-1]) y_distance = choice([0, 1, 2, 3, 4]) y_step = y_direction * y_distance #拒绝原地踏步 if x_step == 0 and y_step == 0: continue #计算下一个点的x和y值 next_x = self.x_value[-1] + x_step next_y = self.y_value[-1] + y_step self.x_value.append(next_x) self.y_value.append(next_y)

rw_visual.py

import  matplotlib.pyplot as plt
#引用同级目录下的文件 from Random_Walk.random_walk import RandomWalk #创建一个RandomWalk的实例 并将其包含的点都绘制出来 rw = RandomWalk() rw.fill_walk() print("test") point_numbers = list(range(rw.num_points)) plt.scatter(rw.x_value,rw.y_value,c=point_numbers, cmap=plt.cm.Blues,edgecolor='none',s=15) # 突出起点和终点 plt.scatter(0, 0, c='green',edgecolors='none',s=100) plt.scatter(rw.x_value[-1], rw.y_value[-1],c='red',edgecolors='none',s=100) # 设置绘图窗口的尺寸 # plt.figure(figsize=(10, 6)) plt.figure(dpi=128, figsize=(10, 6)) # 隐藏坐标轴 # plt.axes().get_xaxis().set_visible(False) # plt.axes().get_yaxis().set_visible(False) plt.show() 

Pygal的学习和使用

安装Pygal

pip3 install pygal

绘制简单的直方图

创建骰子类 die.py

from random import randint class Die(): """表示一个骰子的类""" def __init__(self,num_sides=6): """骰子默认为6面""" self.num_sides = num_sides def roll(self): """返回一个位于1和骰子面数之间的随机值""" return randint(1,self.num_sides)

掷骰子die_visual.py

from  Pygal_learn.die import Die import pygal #创建一个D6 die = Die() #掷几次骰子 并将结果存储在一个列表中 results = [] for roll_num in range(1000): result = die.roll() results.append(result) frequencies = [] #分析结果 for value in range(1,die.num_sides+1): frequency = results.count(value) frequencies.append(frequency) #对结果进行可视化 hist = pygal.Bar() hist.title = "Result of rolling one d6 1000 times" hist.x_labels = ['1','2','3','4','5','6'] hist.x_title = "Result" hist.y_title = "Frequency of result" hist.add("D6",frequencies) hist.render_to_file("die_visual.svg") 

 

使用Web API

安装requests

pip3 install requests

绘制图表

通过抓取GitHub上受欢迎程度最高的Python项目，绘制出图表

import  requests
import  pygal
from pygal.style  import  LightColorizedStyle as LCS,LightenStyle as LS

#执行API调用并存储响应 url = 'https://api.github.com/search/repositories?q=language:python&sort=stars' r = requests.get(url) print("Staus code:",r.status_code) response_dict = r.json() print("Total repositories:", response_dict['total_count']) #探索有关仓库的信息 repo_dicts = response_dict['items'] print('Repositories returned:',len(repo_dicts)) #研究第一个仓库 # repo_dict = repo_dicts[0] # for key in sorted(repo_dict.keys()): # print(key) #研究仓库有关的信息 # Name: macOS-Security-and-Privacy-Guide # Owner: drduh # Stars: 12348 # Repository: https://github.com/drduh/macOS-Security-and-Privacy-Guide # Description: A practical guide to securing macOS. names,plot_dicts = [],[] for repo_dict in repo_dicts: names.append(repo_dict["name"]) # stars.append(repo_dict["stargazers_count"]) plot_dict = { 'value': repo_dict['stargazers_count'], 'label': str(repo_dict['description']), 'xlink': repo_dict['html_url'] } plot_dicts.append(plot_dict) #可视化数据 my_config = pygal.Config() my_config.x_label_rotation = 45 my_config.show_legend = False my_config.title_font_size = 24 my_config.label_font_size = 14 my_config.major_label_font_size = 18 my_config.truncate_label = 15 my_config.show_y_guides = False my_config.width = 1000 my_style = LS('#333366',base_style=LCS) chart = pygal.Bar(my_config,style=my_style) chart.title = "Most-Stared Python Project on Github" chart.x_labels = names print(plot_dicts) chart.add('',plot_dicts) chart.render_to_file('python_repos.svg')

4 从json文件中提取数据，并进行可视化

4.1 数据来源：population_data.json。

4.2 一个简单的代码段：

import json  #导入json模版
filename = 'population_data.png'
with open(filename) as f:
     pop_data = json.load(f)  #加载json文件数据

通过小的代码段了解最基本的原理，具体详情还要去查看手册。

 

4.3制作简单的世界地图（代码如下）

import pygal  #导入pygal

wm = pygal.maps.world.World()  #正确导入世界地图模块
wm.title = 'populations of Countries in North America'
wm.add('North America',{'ca':34126000,'us':309349000,'mx':113423000})

wm.render_to_file('na_populations.svg')  #生成svg文件

结果：

 

4.4 制作世界地图

代码段：

import json

import pygal
from pygal.style import LightColorizedStyle as LCS, RotateStyle as RS

from country_codes import get_country_code

# Load the data into a list.
filename = 'population_data.json'
with open(filename) as f:
    pop_data = json.load(f)

# Build a dictionary of population data.
cc_populations = {}
for pop_dict in pop_data:
    if pop_dict['Year'] == '2010':
        country_name = pop_dict['Country Name']
        population = int(float(pop_dict['Value']))
        code = get_country_code(country_name)
        if code:
            cc_populations[code] = population

# Group the countries into 3 population levels.
cc_pops_1, cc_pops_2, cc_pops_3 = {}, {}, {}
for cc, pop in cc_populations.items():
    if pop < 10000000:                #分组
        cc_pops_1[cc] = pop
    elif pop < 1000000000:
        cc_pops_2[cc] = pop
    else:
        cc_pops_3[cc] = pop

# See how many countries are in each level.
print(len(cc_pops_1), len(cc_pops_2), len(cc_pops_3))

wm_style = RS('#336699', base_style=LCS)
wm = pygal.maps.world.World(style=wm_style)   #已修改，原代码有错误！
wm.title = 'World Population in 2010, by Country'
wm.add('0-10m', cc_pops_1)
wm.add('10m-1bn', cc_pops_2)
wm.add('>1bn', cc_pops_3)

wm.render_to_file('world_population.svg')

辅助代码段country_code.py如下：

from pygal.maps.world import COUNTRIES
from pygal_maps_world import i18n      #原代码也有错误，现已订正

def get_country_code(country_name):
    """Return the Pygal 2-digit country code for the given country."""
    for code, name in COUNTRIES.items():
        if name == country_name:
            return code
    # If the country wasn't found, return None.
    return None

监视API的速率限制

大多数API都存在速率限制，即你在特定时间内可执行的请求数存在限制。要获悉你是否接近了GitHub的限制，请在浏览器中输入https://api.github.com/rate_limit ，你将看到类似于下 面的响应:

参考内容:《Python编程：从入门到实践》