add Day8 homework structured arrays

Author: alvinhuu

D08_structuredArrays/homework.py

@@ -0,0 +1,48 @@
+import numpy as np
+
+# https://numpy.org/doc/stable/reference/arrays.dtypes.html
+# '?'  boolean
+# 'b'  (signed) byte
+# 'B'  unsigned byte
+# 'i'  (signed) integer
+# 'u'  unsigned integer
+# 'f'  floating-point
+# 'c'  complex-floating point
+# 'm'  timedelta
+# 'M'  datetime
+# 'O'  (Python) objects
+# 'S', 'a'  zero-terminated bytes (not recommended)
+# 'U'  Unicode string
+# 'V'  raw data (void)
+
+name_list = ['小明','小華','小菁','小美','小張','John','Mark','Tom']
+sex_list = ['boy','boy','girl','girl','boy','boy','boy','boy']
+weight_list = [67.5,75.3,50.1,45.5,80.8,90.4,78.4,70.7]
+rank_list = [8,1,5,4,7,6,2,3]
+myopia_list = [True,True,False,False,True,True,False,False]
+
+# 將上列 list 依照['name', 'sex', 'weight', 'rank', 'myopia']順序擺入 array，並且資料型態順序擺入[Unicode,Unicode,float,int,boolean]
+# dt=np.dtype('U, U, f, i, ?')
+# dt=np.dtype({'names':(),'formats':()})
+dt=np.dtype({'names':('name', 'sex', 'weight', 'rank', 'myopia'),'formats':('U5', 'U5', 'f', 'i', '?')})
+a=np.zeros(8,dtype=dt)
+a['name']=name_list
+a['sex']=sex_list
+a['weight']=weight_list
+a['rank']=rank_list
+a['myopia']=myopia_list
+print(a)
+
+# 呈上題，將 array 中體重(weight)數據集取出算出全部平均體重
+b=np.average(a['weight'])
+print('全部平均體重 %f' % b)
+
+# 呈上題，進一步算出男生(sex 欄位是 boy)平均體重、女生(sex 欄位是 girl)平均體重
+a_where = np.where(a['sex']=='boy')
+# print(a_where)
+avBoy=np.average( a[a_where]['weight'] )
+print('男生(sex 欄位是 boy)平均體重 %f' % avBoy)
+b_where = np.where(a['sex']=='girl')
+# print(b_where)
+avGirl=np.average( a[b_where]['weight'] )
+print('女生(sex 欄位是 girl)平均體重 %f' % avGirl)