Python学习笔记4

#1.数据可视化
#例1
import matplotlib
import matplotlib.pyplot as plt
input_values = [1,2,3,4,5]
squares = [1,4,9,16,25]
plt.plot(input_values,squares,linewidth=5)\
#plt.title("Square Numbers",fontsize=24)
plt.xlabel("Value",fontsize=14)
plt.ylabel("Square of Value",fontsize=14)
plt.tick_params(axis='both',which='major',labelsize=14) #设置刻度标记的大小
plt.show() #打开matplotlib查看器，并显示绘制的图形

#例2
import matplotlib.pyplot as plt
x = list(range(1,1001))
y = [x_value**2 for x_value in x]
plt.scatter(x,y,s=10,edgecolor='none',c=y) #散点图
plt.axis([0,1100,0,1100000])  #设置每个坐标轴的取值范围
#plt.show() 
plt.savefig('sp.png',bbox_inches='tight') #将图标保存到文件中

#例3(随机漫步)
import matplotlib.pyplot as plt
from random_walk import RandomWalk
#############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):
"""初始化随机漫步的属性"""
self.num_points = num_points
self.x = [0]
self.y = [0] #每次漫步从(0,0)出发

def fill_walk(self):
"""计算随机漫步包含的所有点"""
while len(self.x)<self.num_points:
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

if(x_step==0 and y_step==0): #防止原地踏步
continue

next_x = self.x[-1] + x_step
next_y = self.y[-1] + y_step

self.x.append(next_x)
self.y.append(next_y)
###############################################
rw = RandomWalk()
rw.fill_walk()
plt.figure(dpi=128,figsize=(10,6)) #dpi表示分辨率，制定绘图窗口的尺寸
point_numbers = list(range(rw.num_points))
plt.scatter(rw.x,rw.y,c=point_numbers,cmap=plt.cm.Blues,edgecolor='none',s=15)
plt.scatter(0,0,c='green',edgecolor='none',s=100)             #七起点
plt.scatter(rw.x[-1],rw.y[-1],c='red',edgecolor='none',s=100) #终点
plt.axes().get_xaxis().set_visible(False)  #可见性设为False，即隐藏x轴
plt.axes().get_yaxis().set_visible(False)  #隐藏y轴
plt.show()


#2.下载数据
#例1
import csv #导入csv模块
from matplotlib import pyplot as plt

filename = "sitka_weather_07-2014.csv"
with open(filename) as f:
reader = csv.reader(f)    #创建与文件相关联的阅读器对象
header_row = next(reader) #调用一次，得到文件的第一行
for index,column_header in enumerate(header_row): #enumerate()获取索引及其值
print(index,column_header)
highs = []
for row in reader:
high = int(row[1]) 
highs.append(high) 
print(highs)
fig = plt.figure(dpi=128,figsize=(10,6))
plt.plot(highs,c='red')
plt.show()

#例2
import csv 
from matplotlib import pyplot as plt
from datetime import datetime

first_date = datetime.strptime('2014-7-1','%Y-%m-%d') #转换为相应日期的对象
print(first_date)

filename = "sitka_weather_07-2014.csv"
with open(filename) as f:
reader = csv.reader(f)    #创建与文件相关联的阅读器对象
header_row = next(reader) #调用一次，得到文件的第一行

dates,highs,lows = [],[],[]
for row in reader:
try:
current_date = datetime.strptime(row[0],'%Y-%m-%d')
high = int(row[1]) 
low = int(row[2])
except ValueError:
print(current_date,'missing data')
else:
dates.append(current_date)
highs.append(high)
lows.append(low) 
fig = plt.figure(dpi=128,figsize=(10,6))
plt.plot(dates,highs,c='red',alpha=0.5) #alpha制定颜色的透明度
plt.plot(dates,lows,c='blue',alpha=0.5)
plt.fill_between(dates,highs,lows,facecolor='blue',alpha=0.1) #facecolor填充区域的颜色
fig.autofmt_xdate()
plt.show()

#例3
import json

#将数据加载到一个列表中
filename = 'population_data.json'
with open(filename) as f:
pop_data = json.load(f)

#打印每个国家2010年的人口数量
for pop_dict in pop_data:
if pop_dict['Year'] == '2010':
country_name = pop_dict['Country Name']
population = int(float(pop_dict['Value'])) #因为有些数是小数，不能直接转换为整数
print(country_name + ": " + str(population))

#python -m  pip install --user pygal==1.7 #安装pygal
from pygal.i18n import COUNTRIES
for country_code in sorted(COUNTRIES.keys()):
print(country_code,COUNTRIES[country_code]) #打印国别码


def get_country_code(country_name):
for code,name in COUNTRIES.items():
if name == country_name:
return code
return None #如果没有找到指定的国家就返回None
print(get_country_code('Andorra'))

#3.使用API
#浏览器输入：https://api.github.com/search/repositories?q=language:python&sort=stars
#获取主要语言为Python的仓库信息，并按照获得的星级排序(sort=stars)
#安装requests包：
#pip install --user requests

#例1
import requests
import pygal
from pygal.style import LightColorizedStyle as LCS,LightenStyle as LS
url = 'https://api.github.com/search/repositories?q=language:python&sort=stars'
r = requests.get(url)
print("Status code:",r.status_code)

response_dict = r.json()
print(response_dict.keys())

repo_dicts = response_dict['items']
repo_dict = repo_dicts[0] #第一个仓库
print('\nKeys:',len(repo_dict))
for key in sorted(repo_dict.keys()):
print(key)

print("Selected information about each repository:")
for repo_dict in repo_dicts:
print('\nName:',repo_dict['name'])
print('Owner:',repo_dict['owner']['login'])
print('Stars:',repo_dict['stargazers_count'])
print('Repository:',repo_dict['html_url'])
print('Description:',repo_dict['description'])

names,plot_dicts = [],[]
for repo_dict in repo_dicts:
names.append(repo_dict['name'])
plot_dict = {'value':repo_dict[stargazers_count],'label':repo_dict[description],'xlink':repo_dict['html_url']}
#添加工具提示，label表示鼠标悬停提示，xlink表示单击链接
plot_dicts.append(plot_dict)

#可视化
my_style = LS('#333366',base_style = LCS)
chart = pygal.Bar(style=my_style,x_label_rotation=45,show_legend=False) #条形图，标签旋转45度，隐藏图例
chart.title = 'Most-Starred Python Projects on Github'
chart.x_labels = names
chart.add('',plot_dicts) #标签设置为空字符
chart.render_to_file('python_repos.svg')

#查看搜索API的速率限制：
#浏览器中输入：https://api.github.com/rate_limit

#例2
#浏览器中输入：https://hacker-news.firebaseio.com/v0/item/9884165.json
import requests
from operator import itemgetter

url = 'https://hacker-news.firebaseio.com/v0/item/9884165.json'
r = requests.get(url)
print('Status code:',r.status_code)

submission_ids = r.json()
submission_dicts = []
for submission_id in submission_ids[:30]:
url = ('https://hacker-news.firebaseio.com/v0/item/' + str(submission_id) + '.json')
submission_r = requests.get(url)
print(submission_r.status_code)
response_dict = submission_r.json()

submission_dict = {'title':response_dict['title'],
                  'link':'https://news.ycombinator.com/item?id=' + str(submission_id),
                  'comments':response_dict.get('descendants',0)}
submission_dicts.append(submission_dict)
submission_dicts = sorted(submission_dicts,key=itemgetter('comments'),reverse=True)
for submission_dict in submission_dicts:
print('\nTitle:',submission_dict['title'])
print('Discussion link:',submission_dict['link'])
print('Comments',submission_dict['comments'])