有用的python代码片段有用的python代码片段

打印菱形

法1：

n = 4 for i in range(2*n-1): if i < n: number = 2 * i +1 else: number = 2*(2*n-1-i)-1 print(('*' * number).center(2*n-1, " "))

法2(装逼用的)：

n = 4 _max = 2 * n - 1 a = [("*"*e).center(_max," ")for e in [2*i - 1 if i<=n else 4*n-2*i-1 for i in range(1, _max+1)]] for each in a: print(each)

获取一个目录下最新的文件

import os filelist = os.listdir(path) filelist.sort(key = lambda fn: os.path.getmtime(os.path.join(path, fn))) filelist[-1]#path目录下最新的文件名

同时遍历list元素和下标

myList = ["one", "two", "three"]for i,v in enumerate(myList): print(i, v)

发送各种类型邮件

import smtplib import sys_user = "xxxxx@xxxx.cn" _pwd = "xxxxxx"# jpg类型附件 part = MIMEApplication(open('foo.jpg', 'rb').read()) part.add_header('Content-Disposition', 'attachment', filename="foo.jpg") msg.attach(part) # pdf类型附件 part = MIMEApplication(open('foo.pdf', 'rb').read()) part.add_header('Content-Disposition', 'attachment', filename="foo.pdf") msg.attach(part) # mp3类型附件 part = MIMEApplication(open('foo.mp3', 'rb').read()) part.add_header('Content-Disposition', 'attachment', filename="foo.mp3") msg.attach(part)def sendEmail(sender, receiver, msg): s = smtplib.SMTP("smtp.ym.163.com", 25, timeout=30)# 连接smtp邮件服务器,端口默认是25 s.login(_user, _pwd)# 登陆服务器 s.sendmail(sender, receiver, msg.as_string())# 发送邮件 s.close()

日志配置

import logginglogging.basicConfig(level=logging.DEBUG, format='%(asctime)s - %(levelname)s - %(message)s')

筛选列表中的数据

列表解析

from random import randintdata = https://www.it610.com/article/[randint(-10,10) for _ in range(10)] data_after=[x for x in data if x> 0]

filter函数

from random import randintdata = https://www.it610.com/article/[randint(-10,10) for _ in range(10)] data_after=list(filter(lambda x:x> 0, data))

筛选字典中的数据

字典解析

from random import randintd = {x: randint(60,100) for x in range(1,21)} d_after = {k:v for k,v in d.items() if v > 90}

列表去重

ids = [1,4,3,3,4,2,3,4,5,6,1] ids = list(set(ids))

使用命名元组为每个元素命名

from collections import namedtuple Student = namedtuple('Student', ['name', 'age', 'sex']) s = Student('aaa',18,"male") s2= Student(name='bbb', age=12, sex="female")if s.name == "aaa": pass

统计一个list中各个元素出现的次数

方法1，使用字典

from random import randint data = [randint(1,10) for _ in rang(10)] # 把data里的数据作为key来创建一个字典，且value初始化为0 dic = dict.fromkeys(data, 0) for x in data: dic[x] += 1 #dic 中key为元素，value为该元素出现次数

方法2，使用Counter()

from collections import Counter()data = https://www.it610.com/article/[randint(1,10) for _ in range(10)] # 得到的dic2和方法1的dic一样，一条代码解决问题！ dic2 = Counter(data) # 并且还可以使用most_common(n)方法来直接统计出出现频率最高的n个元素 dic2.most_common(2) # 输出一个list ,其中的元素为（key,value）的键值对，类似[(6, 4), (3, 2)]这样

对字典排序

#以上一例子的dic作为排序对象 dic = {0: 1, 2: 2, 4: 4, 6: 1, 7: 1, -6: 1} dic_after = sorted(dic.items(), key=lambda x:x[1]) # 如果想按key来排序则sorted(dic.items(), key=lambda x:x[0]) # dic_after为一个列表： [(0, 1), (6, 1), (7, 1), (-6, 1), (2, 2), (4, 4)]

使用正则表达式分割文本

import re with open("file.txt") as f text = f.read() # 分割为所有单词组成的list, \W匹配非字母数字及下划线 result = re.split('\W+', text)

使用正则表达式提取文本

import re #用(?P...)括住一个群，并命名为year m = re.search("output_(?P\d{4})", "output_1986.txt") print(m.group("year") #输出1986

启动一个简单的目录服务

$ cd ~/tmp $ python -m SimpleHTTPServer[port] or $ python3 -m http.server[port]

字符串转换为JSON

$ echo '{"job": "developer", "name": "lmx", "sex": "male"}' | python -m json.tool { "job": "developer", "name": "lmx", "sex": "male" }

检查三方库是否正确安装

$ python -c "import paramiko"

使用Python解压zip压缩包

-l 显示zip格式压缩包中的文件列表
-c 创建zip格式压缩包
-e 提取zip格式压缩包
-t 验证文件是一个有效的zip格式压缩包

python -m zipfile -c monty.zip spam.txt eggs.txt python -m zipfile -e monty.zip target-dir/ python -m zipfile -l monty.zip

使用pickle存储对象

使用pickle的dumps()方法可以将对象转换成字符串形式，随后用字节文本形式存储对象到文件

import pickleclass Bird(object): have_feather = Truesummer = Bird() pickle_string = pickle.dumps(summer)with open("summer.pkl", "wb") as f: f.write(pickle_string)

也可以使用dump方法一步到位

import pickleclass Bird(object): have_feather = Truesummer = Bird() with open("summer.pkl", "w") as f: pickle.dump(summer, f)

使用装饰器计算函数运行时间

def decorator_timer(foo): def wrapper(*arg, **karg): t1 = time.time() result = foo(*arg, **karg) t2 = time.time() print(pre+"time:", t2 - t1) return result return wrapper@decorator_timer("@_@") def my_power(a, b): return a**bprint(my_power(2,3)) #输出： #time: 0.0 #5

使用groupby将列表元素分类

from itertools import groupbydef height_class(h): if h> 180: return "tall" elif h<160: return "short" else: return "middle"friends = [191,144,142,170,177,188,293] friends = sorted(friends, key = height_class) for m, n in itertools.groupby(friends, key=height_class): print(m) print(list(n)) #middle #[170, 177] #short #[144, 142] #tall #[191, 188, 293]

使用sets计算交集和差集