python零碎学习

1.两个列表[1,5,7,9]和[2,2,6,8]合并为1,22,5,6,7,8,9]

list1=[1,5,7,9]
list2=[2,2,6,8]
list1.extend(list2)
print(list1)

list1.sort(reverse=False)
print(list1)

输出结果：

2.用datetime模块打印当前时间

import datetime
a=str(datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S'))
print(a)

输出结果：

3.自定义异常的代码

def fn():
    try:
        for i in range(7):
            if i>2:
                raise Exception("数字大于2了")
    except Exception as e:
        print(e)
fn()

输出结果：

4.正则表达式匹配中， (.*)和 (.*?) 匹配区别?

????????????????(.*)是贪婪匹配，会把满足正则的尽可能多的往后匹配
????????????????(*?)是非贪婪匹配，会把满足正则的尽可能少匹配

import re
s = "<a>哈哈</a><a>嘻嘻</a>"
res1 = re.findall("<a>(.*)</a>",s)
print("贪婪匹配",res1)
res2 = re.findall("<a>(.*?)</a>",s)
print("非贪婪匹配",res2)

输出结果：

5.[[1,2],[3,4],[5,6]]一行代码展开该列表得出[1,2,3,4,5,6]

a=[[1,2],[3,4],[5,6]]
x=[j for i in a for j in i]
print(x)

import numpy as np
a=[[1,2],[3,4],[5,6]]
b = np.array(a).flatten().tolist()
print(b)

输出结果：

6.x="abc",y="def",z=["d","e","f"],分别求出xjoin(y)和xjoim(z)返回的结果

x="abc"
y="def"
z=["d","e","f"]
m=x.join(y)
n=x.join(z)
print(m)
print(n)

输出结果：