import numpy as np
l1 = np.arange(24).reshape(4, 6)
print(l1)
print('选择行')
print(l1[2])
print('选择列')
print(l1[:, 1])
print('选择不连续的行列')
print(l1[[3, 2], [2, 4]])
print('选择连续行列')
print(l1[1:, 2:4])
print('索引')
print(l1[2, 3])
print('布尔索引')
print(l1[l1 < 10])
print(l1)
print('赋值')
l1[0, 0] = 0
print(l1)
print('三元运算符')
print(np.where(l1 < 10, 0, 10))
print('剪裁')
print(l1.clip(10, 20))
print('数组转置')
print(l1.T)
print(l1.transpose())
print(l1.swapaxes(1, 0))
print('读取本地文件')
print("a = np.loadtxt('路径', delimiter=',', dtype='int')")
print('nan的用法')
l1 = l1.astype(float)
print(l1)
l1[[2, 2], [3, 4]] = np.nan
print(l1)
print('统计数组中nan的个数')
print(np.count_nonzero(l1 != l1))
print('将数组中nan替换')
l1[np.isnan(l1)] = 15, 16
print(l1)
print(l1.sum(axis=0))
print(l1.sum(axis=1))
print(l1)
print(l1.mean(axis=0), '均值')
print(l1.max(), '最大值')
print(l1.min(), '最小值')
print(np.median(l1, axis=0), '中值')
print(np.ptp(l1), '最大值和最小值的差，极值')
