import numpy as np

student = np.zeros(3, dtype={'names':('name', 'age', 'score'), 'formats':('U10', 'i4', 'f8')})

dtype = [('name', 'U10'), ('age', 'i4'), ('score', 'f8')]

student['name'] = ['Alice', 'Bob', 'Chris']
student['age'] = [22, 24, 26]
student['score'] = [89.6, 92.8, 87.2]

print(student)

[('Alice', 22, 89.6) ('Bob', 24, 92.8) ('Chris', 26, 87.2)]

print(student[0])

('Alice', 22, 89.6)

average_score = np.mean(student['score'])
print(average_score)

89.86666666666666

sorted_student = np.sort(student, order='score')[::-1]
print(sorted_student)

[('Bob', 24, 92.8) ('Alice', 22, 89.6) ('Chris', 26, 87.2)]

N = 1000000

# 使用Numpy结构化数组来存储数据
person = np.zeros(N, dtype={'names':('name', 'age', 'weight'), 'formats':('U10', 'i4', 'f8')})
person['name'] = np.random.choice(['Alice', 'Bob', 'Chris'], N)
person['age'] = np.random.randint(low=18, high=40, size=N)
person['weight'] = np.random.normal(loc=70, scale=10, size=N)

# 使用Python列表来存储数据
person_lst = []
for i in range(N):
    person_lst.append({'name': np.random.choice(['Alice', 'Bob', 'Chris']),
                       'age': np.random.randint(low=18, high=40),
                       'weight': np.random.normal(loc=70, scale=10)})

# 使用Numpy计算结构化数组的平均体重
start_time = time.time()
np.mean(person['weight'])
end_time = time.time()
print(f"numpy structure array time: {end_time - start_time} seconds")

# 使用Python计算列表的平均体重
start_time = time.time()
sum_weight = 0
for i in range(N):
    sum_weight += person_lst[i]['weight']
average_weight = sum_weight / N
end_time = time.time()
print(f"python list time: {end_time - start_time} seconds")

numpy structure array time: 0.00032019615173339844 seconds
python list time: 0.6255552768707275 seconds