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python列表(list)反序(降序)的实现方式:原址反序,list.reverse()、list.sort()、全数组遍历、1/2数组遍历;新生成列表,resersed()、sorted
python列表(list)反序(降序)的实现方式:原址反序,list.reverse()、list.sort()、全数组遍历、1/2数组遍历;新生成列表,resersed()、sorted()、负步长切片[::-1]。共七种方式,可以实现列表反序。
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lis = list('abcdefghijklmnopqrstuvwxyz')print(f"\n\n序列:{lis}\n")
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
可以利用列表方法,直接反序。reverse方法无返回值,原址操作列表。
lis = list('abcdefghijklmnopqrstuvwxyz')lis.reverse() # reverse方法无返回值,原址反序操作列表。print(f"\n\n序列:{lis}\n\n反序:{lis}\n")
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
反序:[‘z’, ‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
sort()方法无返回值,原址排序操作列表。其reverse参数默认=False,正序排序;令其=True,反序(降序)排序。
lis = list('abcdefghijklmnopqrstuvwxyz')lis.sort(reverse=True) # sort方法无返回值,原址排序操作列表。print(f"\n\n序列:{lis}\n\n反序:{lis}\n")
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
反序:[‘z’, ‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
用list.pop()模拟栈弹出,将弹出元素用list.insert()方法依次插入列表0~n-1位置,实现反序。
lis = list('abcdefghijklmnopqrstuvwxyz')for i in range(len(lis)): lis.insert(i, lis.pop())print(f"\n\n序列:{lis}\n\n反序:{lis}\n")
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
反序:[‘z’, ‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
从列表中间开始,依次对调前后元素实现反序。这要区分处理列表元素为奇偶的情况:奇,中间位置只有一个元素,不;偶,对调从处中间的两个元素开始对调。
数组元素总数为奇数,中间位置n=int(len(lis)/2)m,只有一个元素,不用对调。对调从下标n-1、n+1开始对调。
lis = list('abcdefghijklmnopqrstuvwxy')n = int(len(lis)/2) # 计算中间位置。for i in range(n+1): print(lis[n-i], lis[1, n+i]) lis[n-i], lis[n+i] = lis[n+i], lis[n-i]print(f"\n\n序列:{lis}\n\n反序:{lis}\n")
l n
k o
j p
i q
h r
g s
f t
e u
d v
c w
b x
a y
序列:[‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
反序:[‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
数组元素总数为偶数,中间位置n=int(len(lis)/2)±1之间,没有元素。对调从下标n-0、n+0开始对调。
n = int(len(lis)/2) - 1 # 计算中间位置。lis = list('abcdefghijklmnopqrstuvwxyz')n = int(len(lis)/2) - 1 # 计算中间位置。for i in range(n+1): print(lis[n-i], lis[n+i+1]) lis[n-i], lis[n+i+1] = lis[n+i+1], lis[n-i]print(f"\n\n序列:{lis}\n\n反序:{lis}\n")
m n
l o
k p
j q
i r
h s
g t
f u
e v
d w
c x
b y
a z
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
反序:[‘z’, ‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
直接用[::-1]切片原列表,生成的新列表即已反序。
了解“切片”更多知识点,可以点击我的学习笔记“Python之魔幻切片”。
lis = list('abcdefghijklmnopqrstuvwxyz')print(f"\n\n序列:{lis}\n\n反序:{lis[::-1]}\n")
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
反序:[‘z’, ‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
效果同list.reverse()方法,不同的是reversed()函数不是原址操作列表,而是返回一个新列表。
lis = list('abcdefghijklmnopqrstuvwxyz')print(f"\n返回类型:{type(reversed(lis))}\n")print(f"\n\n序列:{lis}\n\n反序:{list(reversed(lis))}\n")
返回类型:
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
反序:[‘z’, ‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
效果同list.sort()方法,不同的是sorted()函数不是原址操作列表,而是返回一个新列表。
lis = list('abcdefghijklmnopqrstuvwxyz')print(f"\n返回类型:{type(sorted(lis, reverse=True))}\n")print(f"\n\n序列:{lis}\n\n反序:{sorted(lis, reverse=True)}\n")
返回类型:
序列:[‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’]
反序:[‘z’, ‘y’, ‘x’, ‘w’, ‘v’, ‘u’, ‘t’, ‘s’, ‘r’, ‘q’, ‘p’, ‘o’, ‘n’, ‘m’, ‘l’, ‘k’, ‘j’, ‘i’, ‘h’, ‘g’, ‘f’, ‘e’, ‘d’, ‘c’, ‘b’, ‘a’]
#!/sur/bin/nve # coding: utf-8 # reverse()lis = list('abcdefghijklmnopqrstuvwxyz')lis.reverse() # reverse方法无返回值,原址反序操作列表。print(f"\n\n序列:{lis}\n\n反序:{lis}\n")input(' reverse()方法 '.center(48, '~'))# sort()lis = list('abcdefghijklmnopqrstuvwxyz')lis.sort(reverse=True) # sort方法无返回值,原址排序操作列表。print(f"\n\n序列:{lis}\n\n反序:{lis}\n")input(' sort()方法 '.center(48, '~'))# for alllis = list('abcdefghijklmnopqrstuvwxyz')for i in range(len(lis)): lis.insert(i, lis.pop())print(f"\n\n序列:{lis}\n\n反序:{lis}\n")input(' 遍历数组所有元素 '.center(42, '~'))# for 1/2,奇数个元素数组lis = list('abcdefghijklmnopqrstuvwxy')n = int(len(lis)/2) # 计算中间位置。for i in range(1, n+1): print(lis[n-i], lis[n+i]) lis[n-i], lis[n+i] = lis[n+i], lis[n-i]print(f"\n\n序列:{lis}\n\n反序:{lis}\n")input(' 遍历数组1/2元素(总元素为奇数) '.center(38, '~'))# for all,偶数个元素数组。lis = list('abcdefghijklmnopqrstuvwxyz')n = int(len(lis)/2) - 1 # 计算中间位置。for i in range(n+1): print(lis[n-i], lis[n+i+1]) lis[n-i], lis[n+i+1] = lis[n+i+1], lis[n-i]print(f"\n\n序列:{lis}\n\n反序:{lis}\n")input(' 遍历数组1/2元素(总元素为偶数) '.center(38, '~'))# 新生成列表,负步长切片。lis = list('abcdefghijklmnopqrstuvwxyz')print(f"\n\n序列:{lis}\n\n反序:{lis[::-1]}\n")input(' 负步长切片 '.center(45, '~'))# 新生成列表,resersed()。lis = list('abcdefghijklmnopqrstuvwxyz')print(f"\n返回类型:{type(reversed(lis))}\n")print(f"\n\n序列:{lis}\n\n反序:{list(reversed(lis))}\n")input(' reversed()函数 '.center(48, '~'))# 新生成列表,storted()。lis = list('abcdefghijklmnopqrstuvwxyz')print(f"\n返回类型:{type(sorted(lis, reverse=True))}\n")print(f"\n\n序列:{lis}\n\n反序:{sorted(lis, reverse=True)}\n")input(' sorted()函数 '.center(48, '~'))
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全栈领域优质创作者——寒佬(还是国内某高校学生)博文“非技术文—关于英语和如何正确的提问”,“英语”和“会提问”是学习的两大利器。
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来源地址:https://blog.csdn.net/m0_57158496/article/details/128271700
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