Sample Code/Day_05_SampleCode_v2.ipynb

{"nbformat":4,"nbformat_minor":0,"metadata":{"kernelspec":{"display_name":"Python 3","language":"python","name":"python3"},"language_info":{"codemirror_mode":{"name":"ipython","version":3},"file_extension":".py","mimetype":"text/x-python","name":"python","nbconvert_exporter":"python","pygments_lexer":"ipython3","version":"3.6.5"},"colab":{"name":"05 Example.ipynb","provenance":[]}},"cells":[{"cell_type":"markdown","metadata":{"id":"6h-WgV39ONYX"},"source":["# 範例\n","***"]},{"cell_type":"markdown","metadata":{"id":"-xhRK_JYONYi"},"source":["# [教學目標]\n","\n","* 正確的使用 NumPy 中的比較與邏輯運算\n","* 掌握 NumPy 陣列的遮罩特性與使用\n","* 知道 NumPy 陣列與 Python 列表的用法差異\n","\n","\n"]},{"cell_type":"code","metadata":{"id":"VL_zfVEMONYj","outputId":"49130b79-8b5e-49d3-e815-32e7587c630f"},"source":["# 載入 NumPy 套件\n","import numpy as np\n","\n","# 檢查正確載入與版本\n","print(np)\n","print(np.__version__)"],"execution_count":null,"outputs":[{"output_type":"stream","text":["<module 'numpy' from '/Users/wei/.virtualenvs/py3/lib/python3.6/site-packages/numpy/__init__.py'>\n","1.16.1\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"Im70sam2ONYk","outputId":"472c277c-9530-4739-c551-24e392dc0219"},"source":["# 陣列中的比較運算\n","\n","a = np.array( [20,30,40,50] )\n","b = np.arange( 4 )\n","\n","print(a > b) # [ True  True  True  True]\n","print(a < b) # [False False False False]\n","print(a == b) # [False False False False]\n","print(a != b) # [ True  True  True  True]\n"],"execution_count":null,"outputs":[{"output_type":"stream","text":["[ True  True  True  True]\n","[False False False False]\n","[False False False False]\n","[ True  True  True  True]\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"XZCzytfEONYm","outputId":"bacf6610-3efc-41da-82f3-db3a4cbffb0b"},"source":["# 陣列中的邏輯運算\n","\n","import numpy as np\n","\n","a = np.array( [True, True, False, False] )\n","b = np.array( [True, False, True, False]  )\n","\n","print(a and b)\n"],"execution_count":null,"outputs":[{"output_type":"error","ename":"ValueError","evalue":"The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()","traceback":["\u001b[0;31m----------------------------------------------------------------------\u001b[0m","\u001b[0;31mValueError\u001b[0m                           Traceback (most recent call last)","\u001b[0;32m<ipython-input-4-55f88f2d97bb>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      6\u001b[0m \u001b[0mb\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mnp\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0marray\u001b[0m\u001b[0;34m(\u001b[0m \u001b[0;34m[\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;32mFalse\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;32mFalse\u001b[0m\u001b[0;34m]\u001b[0m  \u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      7\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 8\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0ma\u001b[0m \u001b[0;32mand\u001b[0m \u001b[0mb\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m","\u001b[0;31mValueError\u001b[0m: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()"]}]},{"cell_type":"code","metadata":{"id":"njBQ8_IkONYm","outputId":"8b16df59-4ffb-47f6-b068-44d2424a6c34"},"source":["a = np.array( [True, True, False, False] )\n","b = np.array( [True, False, True, False]  )\n","\n","print(a & b) # [ True False False False]\n","print(a | b) # [ True  True  True False]\n"],"execution_count":null,"outputs":[{"output_type":"stream","text":["[ True False False False]\n","[ True  True  True False]\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"tqn-DyLgONYn","outputId":"ec1358c2-487f-428c-c90c-55d4f0da98e1"},"source":["# 利用布林值作為篩選的條件：遮罩\n","\n","import numpy as np\n","\n","a = np.array( [10, 20, 30, 40] )\n","\n","print(a[ [True, True, True, True] ])\n","print(a[ [True, False, True, False] ])\n","print(a[ [False, False, False, False] ])\n"],"execution_count":null,"outputs":[{"output_type":"stream","text":["[10 20 30 40]\n","[10 30]\n","[]\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"M3sDHwaKONYo","outputId":"9335c6d5-c870-4a45-cf76-082f5741490e"},"source":["# 從比較/邏輯運算到遮罩特性\n","\n","import numpy as np\n","\n","a = np.array( [10, 20, 30, 40] )\n","\n","print(a > 20)\n","print(a[ [False, False, True, True] ])\n","print(a[ a > 20 ])\n"],"execution_count":null,"outputs":[{"output_type":"stream","text":["[False False  True  True]\n","[30 40]\n","[30 40]\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"WwvZYavxONYo","outputId":"3169ccc4-b55f-4fb2-c1d4-cc2f2731a75f"},"source":["# 遮罩特性背後的強大之處\n","\n","a = np.arange( 4 )\n","print(a[a > 1])\n","\n","a = np.arange( 4 )\n","b = []\n","for i in a:\n","    if i > 1:\n","        b.append(i)\n","print(b)\n"],"execution_count":null,"outputs":[{"output_type":"stream","text":["[2 3]\n","[2, 3]\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"XGHltEQAONYp","outputId":"7253b646-43d8-46b1-ea02-3b44ee0c2bf0"},"source":["# 補充：any() 和 all()\n","\n","print(np.any([True, True, True]))\n","print(np.any([True, False, False]))\n","print(np.any([False, False, False]))\n"],"execution_count":null,"outputs":[{"output_type":"stream","text":["True\n","True\n","False\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"HndORgTxONYp","outputId":"3a8cb8e4-2a90-44c3-935e-38644a1a95a5"},"source":["\n","print(np.all([True, True, True]))\n","print(np.all([True, False, False]))\n","print(np.all([False, False, False]))\n"],"execution_count":null,"outputs":[{"output_type":"stream","text":["True\n","False\n","False\n"],"name":"stdout"}]},{"cell_type":"code","metadata":{"id":"43Ocf4qyONYq"},"source":[""],"execution_count":null,"outputs":[]}]}