Python 数组.切片
Numpy 切片(Slicing):
arr = arr[ slice( 2, 7, 2 ) ] , # 写法1
arr = arr[ 2 : 7 : 2] # 写法2 , 从索引 2 开始到索引 7 停止,间隔为 2
nums = list(range(5)) # range is a built-in function that creates a list of integers
print(nums) # Prints "[0, 1, 2, 3, 4]"
# index Min to Max 或者 0 ~ Max
nums[:] # [0, 1, 2, 3, 4]
nums[2:4] # [2, 3] index 2 to 4
nums[2:] # [2, 3, 4] index 2 to Max
nums[:2] # [0, 1] index Min to 2 或者 0 ~ 2
# ‘无符号” 情况为索引下标,
# ‘有 - 符号’情况为最大下标 - 去的值,逆推)
nums[:-1] # [0, 1, 2, 3]
# 赋值
nums[2:4] = [8, 9] # Assign a new sublist to a slice
print(nums) # Prints "[0, 1, 8, 9, 4]"
print("--常规操作( 二维)-------------")
# index 2 to 4
nums[ 第一维 ,第二维]
nums[ :3 , : ] ) # 所有
print("--非常规( `-` 代表从后向前计算位置 )-------------")
nums = list(range(5))
nums[:-1] # [0, 1, 2, 3]
nums[:-2] # [0, 1, 2]
nums[:-3] # [0, 1]
nums[:-4] # [0]
nums[:-5] # []
print("--非常规-------------")
nums[-1:] # [4]
nums[-2:] # [3, 4]
nums[-3:] # [2, 3, 4]
nums[-4:] # [1, 2, 3, 4]
nums[-5:] # [0, 1, 2, 3, 4]