索引
python比较神奇,可以从正面数或反着数,每一个位置都有自己的下标
切片
假设现在有一阵列
a = [1, 2, 3, 4, 5]
print(a[0:4:2])
# [1, 3, 5]
# a是阵列的名称
# []里面的第一个数字是起点(start)
# 第二个是终点(end)
# 第三个是间隔(step)
a = [1, 2]
b = [3, 4]
print(a + b)
# [1, 2, 3, 4]
a = [1, 3, 5]
print(5 in a)
# True
a = [1, 3, 5, 7, 9]
print(len(a), max(a), min(a))
# 5 9 1
# 直接创建
name = [element1, element2, ...]
# 创建空阵列
name = []
# 使用list()函数
nums = list(range(10))
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
name = [1, 2]
del name
name = [1, 2, 3]
print(name[2])
# 3
name = [1, 2, 3, 4]
# 使用for回圈
for item in name:
print(item, end = '')
# 使用for回圈和enumerate()函数
for index, item in enumerate(name):
print(index, item)
# append()是加在屁股後面的
name = [1, 2, 3]
name.append(4)
print(name)
# [1, 2, 3, 4]
# 也可以使用insert(),但效率不高,不推荐使用
# 使用extend()将2个阵列加在一起
name2 = [5, 6]
print(name.extend(name2))
[1, 2, 3, 4, 5, 6]
name = [0, 1, 3, 3]
name[2] = 2
print(name)
#[0, 1, 2, 3]
name = [0, 1, 2, 3]
# 根据index值
del name[3]
# [0, 1, 2]
# 根据元素值
name.remove(2)
# [0, 1]
nums = [0, 1, 1, 2, 3, 3]
print(nums.count(1))
# 2
# index(object)
nums = [0, 1, 1, 2, 3]
answer = nums.index(1)
print(answer)
# 1
# sum(listname[, start])
nums = [0, 1, 2, 3]
answer = sum(nums)
print(answer)
# 6
# namelist.sort(key = None, reverse = True)
# key是比较的键(值)
# reverse则可指定是升序或降序
nums = [0, 5, 1, 2, 3, 4]
nums = nums.sort()
print(nums)
# [0, 1, 2, 3, 4, 5]
nums = nums.sort(reverse = False)
print(nums)
# [5, 4, 3, 2, 1, 0]
# 简单明了的意思是把sort()反过来看就好
nums = [0, 2, 5, 6, 1]
nums = sorted(nums)
print(nums)
# [0, 1, 2, 5, 6]
# list = [表达式 for 循环变量 in range()]
nums = [i for i i in range(10)]
print(nums)
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
# list = [表达式 for 循环变量 in 原阵列]
nums = [0, 1, 2, 3]
new_nums = [x*0.5 for x in nums]
print(new_nums)
# [0.0, 0.5, 1.0, 1.5]
nums = [0, 1, 2, 3, 5, 9]
new_nums = [x for x in nums if x % 3 == 0]
print(new_nums)
# [0, 3, 9]
# [[00, 01, 02, 03],
# [10, 11, 12, 13],......]
test = []
for i in range(4):
test.append([])
for j in range(5):
test[i].append(j)
print(test)
# [[0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4]]
nums = [[i for i in range(5)] for j in range(4)]
print(nums)
# [[0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4]]
# 是(),不是[],[]是阵列非元组
nums = (1, 2, 3)
# 其实未必要用(),用 , 隔开就可以了
nums = '0', '1', '2'
print(nums)
# ('0', '1', '2')
empty = ()
# tuple(data)
nums = tuple(range(0, 5, 2))
print(nums)
# (0, 2, 4)
# 直接删除即可
nums = (0, 1, 2)
del nums
nums = (0, 1, 2)
print(nums[0])
# 0
print(nums[0:2])
# (0, 1)
nums = (0, 1, 2)
nums = (1, 2)
print(nums)
# (1, 2)
nums = (0, 1, 2)
add_nums = (3, 4)
print(nums + add_nums)
# (0, 1, 2, 3, 4)
import random
nums = (random.randint(10, 100) for i in range(10))
print(nums)
# <generator object <genexpr> at 0x0000016C21DD8190>
这边还需要一个tuple,因为元组推导式生成的结果不是一个元组,所以还需要转换
加上
nums = tuple(nums)
print(nums)
# (24, 23, 59, 81, 35, 46, 18, 60, 89, 87)
nums = (i for i in range(3))
print(nums.__next__())
# 0
print(nums.__next__())
# 1
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