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# -*- coding:utf-8 -*-
# author:
import numpy
'''where函数的使用'''
cond = numpy.array([True,False,True,False])
x = numpy.where(cond,-2,2)
print(x) # [-2  2 -2  2]
cond = numpy.array([1,2,3,4])
x = numpy.where(cond>2,-2,2)
print(x) # [ 2  2 -2 -2]
y1 = numpy.array([-1,-2,-3,-4])
y2 = numpy.array([1,2,3,4])
x = numpy.where(cond>2,y1,y2) # 长度须匹配
print(x) # [1,2,-3,-4]
 
'''where函数的嵌套使用'''
y1 = numpy.array([-1,-2,-3,-4,-5,-6])
y2 = numpy.array([1,2,3,4,5,6])
y3 = numpy.zeros(6)
cond = numpy.array([1,2,3,4,5,6])
x = numpy.where(cond>5,y3,numpy.where(cond>2,y1,y2))
print(x) # [ 1.  2. -3. -4. -5.  0.]