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转置矩阵
old_list = [[1, 2, 3], [3, 4, 6], [5, 6, 7]]
list(list(x) for x in zip(*old_list))
[[1, 3, 5], [2, 4, 6], [3, 6, 7]]
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② 二进制转十进制
decimal = int(‘1010’, 2)
print(decimal) #10
10
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③ 字符串大写转小写
方法一 lower()
“Hi my name is Allwin”.lower()
‘hi my name is allwin’
方法二 casefold()
“Hi my name is Allwin”.casefold()
‘hi my name is allwin’
‘hi my name is allwin’
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④ 字符串小写转大写
“hi my name is Allwin”.upper()
‘HI MY NAME IS ALLWIN’
‘HI MY NAME IS ALLWIN’
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⑤ 将字符串转换为字节
“convert string to bytes using encode method”.encode()
b’convert string to bytes using encode method’
b’convert string to bytes using encode method’
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⑥ 复制文件内容
import shutil; shutil.copyfile(‘source.txt’, ‘dest.txt’)
‘dest.txt’
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⑦ 快速排序
qsort = lambda l : l if len(l)<=1 else qsort([x for x in l[1:] if x < l[0]]) + [l[0]] + qsort([x for x in l[1:] if x >= l[0]])
qsort([1,3,2])
[1, 2, 3]
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⑧ n 个连续数之和
n = 3
sum(range(0, n+1))
6
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⑨ 交换两个变量
a=1
b=2
a,b = b,a
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⑩ 斐波那契数列
fib = lambda x: x if x<=1 else fib(x-1) + fib(x-2)
fib(10)
55
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? 将嵌套列表合并为一个列表
main_list = [[1,2],[3,4],[5,6,7]]
[item for sublist in main_list for item in sublist]
[1, 2, 3, 4, 5, 6, 7]
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? 运行 HTTP 服务器
python3 -m http.server 8000
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? 反转列表
numbers = ‘I Love China’
numbers[::-1]
‘anihC evoL I’
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? 返回阶乘
import math; fact_5 = math.factorial(5)
fact_5
120
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? 判断列表推导式
even_list = [number for number in [1, 2, 3, 4] if number % 2 == 0]
even_list
[2, 4]
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? 取最长字符串
words = [‘This’, ‘is’, ‘a’, ‘list’, ‘of’, ‘words’]
max(words, key=len)
‘words’
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? 列表推导式
li = [num for num in range(0,100)]
this will create a list of numbers from 0 to 99
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? 集合推导式
num_set = { num for num in range(0,100)}
this will create a set of numbers from 0 to 99
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? 字典推导式
dict_numbers = {x:x*x for x in range(1,5) }
{1: 1, 2: 4, 3: 9, 4: 16}
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? if-else
print(“even”) if 4%2==0 else print(“odd”)
even
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? 无限循环
while 1:0
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? 检查数据类型
isinstance(2, int)
isinstance(“allwin”, str)
isinstance([3,4,1997], list)
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? while 循环
a=5
while a > 0: a = a - 1; print(a)
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? 使用 print 语句写入到文件里
print(“Hello, World!”, file=open(‘source.txt’, ‘w’))
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? 统计字频
print(“umbrella”.count(‘l’))
2
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? 合并两个列表
list1.extend(list2)
contents of list 2 will be added to the list1
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? 合并两个字典
dict1.update(dict2)
contents of dictionary 2 will be added to the dictionary 1
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? 合并两个集合
set1.update(set2)
contents of set2 will be copied to the set1
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? 时间戳
import time; print(time.time())
1632146103.8406303
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? 统计最多的元素
test_list = [9, 4, 5, 4, 4, 5, 9, 5, 4]
most_frequent_element = max(set(test_list), key=test_list.count)
most_frequent_element
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