導入必要的第三方庫

from requests import get

import matplotlib.pyplot as plt

/usr/lib/python3/dist-packages/matplotlib/font_manager.py:273: UserWarning: Matplotlib is building the font cache using fc-list. This may take a moment.
  warnings.warn('Matplotlib is building the font cache using fc-list. This may take a moment.')
/usr/lib/python3/dist-packages/matplotlib/font_manager.py:273: UserWarning: Matplotlib is building the font cache using fc-list. This may take a moment.
  warnings.warn('Matplotlib is building the font cache using fc-list. This may take a moment.')

from dateutil import parser

url = 'https://apex.oracle.com/pls/apex/raspberrypi/weatherstation/getallmeasurements/505307'

weather = get(url).json()

weather['items'][0]['ambient_temp']

9.77

weather['items'][0]

{'air_pressure': 982.51,
 'air_quality': 75.82,
 'ambient_temp': 9.77,
 'created_by': 'Test Brompton Academy',
 'created_on': '2016-11-19T22:50:00Z',
 'ground_temp': -1000,
 'humidity': 71.11,
 'id': 1707846,
 'rainfall': 0,
 'reading_timestamp': '2016-11-19T22:50:00Z',
 'updated_by': 'Test Brompton Academy',
 'updated_on': '2016-11-20T00:56:09.435Z',
 'weather_stn_id': 505307,
 'wind_direction': 111.92,
 'wind_gust_speed': 22.8,
 'wind_speed': 12.34}

迭代天氣數據集，取出溫度數據，并且保存到列表

利用for循環獲取溫度列表

temperatures = []
for record in weather['items']:
    temperature = record['ambient_temp']
    temperatures.append(temperature)

利用列表生成式來獲取溫度數據

temperatures = [record['ambient_temp'] for record in weather['items']]

把RaspberryPi的數據庫所用的日期轉換成Python中的datetime對象格式

parser.parse(weather['items'][0]['reading_timestamp'])

datetime.datetime(2016, 11, 19, 22, 50, tzinfo=tzutc())

用列表生成式來獲取日期列表

timestamps = [parser.parse(record['reading_timestamp']) for record in weather['items']]

繪制圖像

1. 繪圖需要的代碼很少，首先聲明繪圖要用的數據集合，然后第二個用來展示數據：

## 繪制溫度時間變化圖
plt.plot(timestamps, temperatures)
plt.ylabel('溫度')
plt.xlabel('時間')
plt.show()

到此為止教程結束

拓展思考

1. 比如物理的加速度實驗，用紙袋獲取數據后可以用這種方法繪圖
2. 生物實驗觀測的數據繪圖
3. 數學圖像，統計觀察

如果是實際實驗獲得的數據，獲取數據的過程可以大大簡化，這樣只需要8行左右的代碼就可以繪制一些實驗曲線