python实例
1. 两个有序数列合并为1个有序数列
# -*- coding:utf-8 -*- #两个有序数列合并为1个有序数列 str1 = [1,2,5,7,9] str2 = [2,3,4,4.1,4.2,4.3,4.4] def merge(str1,str2): merge_str = [] len1 = len(str1) len2 = len(str2) i = 0 j = 0 while i < len1 and j < len2: if str1[i] <= str2[j]: merge_str.append(str1[i]) i +=1 else: merge_str.append(str2[j]) j +=1 if i < len1: for z in range(i+1,len1): merge_str.append(str1[z]) if j < len2: for z in range(j+1,len2): merge_str.append(str2[z]) return merge_str
print merge(str1,str2)
2.字典和列表读取速度测试
# coding:utf-8 #字典和列表的区别，列表是根据偏移量来读取的，字典是根据键的Hash来读取的 import time testDict = {} testList = [] for i in range(10000000): n = str(i) testDict[n] = i testList.append(n) startTime = time.time() if '1002231' in testDict: print 'yes' print time.time()-startTime startTime = time.time() if '1002231' in testList: print 'yes' print time.time()-startTime
3.冒泡排序
冒泡排序原理: 每一趟只能将一个数归位, 如果有n个数进行排序,只需将n-1个数归位, 也就是说要进行n-1趟操作(已经归位的数不用再比较)
# -*- coding:utf-8 -*- def sort(num): for i in range(len(num)-1): #负责设置冒泡排序进行的次数 for j in range(len(num)-1-i): #ｊ为列表下标 if num[j] > num[j+1]: num[j],num[j+1] = num[j+1],num[j] return num num1 = [3,2,1,6,1] print sort(num1)
4.倒叙输出原字符串
# -*- coding:utf-8 -*- str1 = "python" new_str = [] for i in range(len(str1)-1,-1,-1): new_str.append(str1[i]) print ' '.join(new_str) #print new_str
5.统计字符串中出现最多的字符
# -*- coding:utf-8 -*- def count(str1): Dic = {} maxnum = 0 for i in str1: if i in Dic: Dic[i] = Dic[i]+1 else: Dic.setdefault(i,1) for key,value in Dic.items(): if Dic[key] > maxnum: maxnum = Dic[key] letter = key return letter,maxnum str1 = "pythonpp" print count(str1)
6.遍历指定路径下的所有文件
# -*- coding:utf-8 -*- import os # 枚举dirPath目录下的所有文件 # os.walk(top[, topdown=True[, onerror=None[, followlinks=False]]]) # top -- 是你所要遍历的目录的地址, 返回的是一个三元组(root,dirs,files) # root 所指的是当前正在遍历的这个文件夹的本身的地址(所有的根地址) # dirs 是一个 list ，内容是该文件夹中所有的目录的名字(不包括子目录) # files 同样是 list , 内容是该文件夹中所有的文件(不包括子目录) def main(fileDir): for root, dirs, files in os.walk(fileDir): print "root:" + root for dir in dirs: print(os.path.join(root, dir)) for file in files: print(os.path.join(root, file)) if __name__ == '__main__': file = r"E:\A" print main(file)
7.continue和break
#-*- coding:utf-8 -*- i = 0 while i < 6: i +=1 for j in range(4): #print j, # print "j","=",j if j == 2: break #彻底跳出循环 print "j","=",j for k in range(4): if k == 2: continue #略下本次循环的剩余内容，直接进入下一次循环 #print k, print "k","=",k if i > 3: break #当I>3,跳出，后续的i不再输出 #print i, print "i","=",i
8.求和运算（奇数和、偶数和）
#-*- coding:utf-8 -*- sum = 0 for i in range(1,101): sum = sum + i print sum sum1 = 0 for i in range(1,101,2): sum1 = sum1 + i print sum1 sum2 = 0 for i in range(0,101,2): sum2 = sum2 + i print sum2
9. join()方法
join() 方法用于将序列中的元素以指定的字符连接生成一个新的字符串。
s = ["apple","pear","orange"] fruit = ".".join(s) print fruit
返回结果：
apple.pear.orange
10.输入多行内容，并将输入结果写入到指定文件
#-*- coding:utf-8 -*- #os.linesep字符串给出当前平台使用的行终止符。例如，Windows使用'\r\n'，Linux使用'\n'而Mac使用'\r'。 import os def WriteFile(filename): fp = open(filename,"a") print "\r请输入多行文字","(输入.号回车保存)" while True: content = raw_input("content:") if content == ".": break else: fp.write("%s%s" %(content,os.linesep)) fp.close() if __name__ == "__main__": WriteFile(r"F:\AONE\test.txt")
11.读写文件
#-*- coding:utf-8 -*- spath=r"F:\AONE\test.txt" f=open(spath,"w") f.write("First line 1.\n") f.writelines("First line 2.\n") f.close() f=open(spath,"r") lines = f.readlines() for line in lines: print line.strip() # for line in f: # print("每一行的数据是:%s" %line) f.close()
12．魔法方法
构造方法： __init__,对于子类的构造方法，需要调用父类的构造方法，有以下两种调用方式：
#-*- coding:utf-8 -*- class bird: def __init__(self): self.hungry = False def eat(self): if self.hungry: print 'Aaaaa...' self.hungry = False else: print 'No,thanks!' class songbird(bird): def __init__(self): #如果重写了构造方法，需要调用父类的构造方法 #(1)方法1:未绑定方法，通过类名调用,将self传递过去 bird.__init__(self) #(2)#方法2：super函数，参数类和对象做参数,再调用父类init函数 super(SongBird, self).__init__() self.sound = 'Squawk!' def sing(self): print self.sound if __name__ == "__main__": A = songbird() print A.sing() print A.eat()
13．简单的数据库应用程序（shelve）
#-*- coding:utf-8 -*- import sys,shelve ''' shelve模块比pickle模块简单，只有一个open函数，返回类似字典的对象，可读可写：key必须为字符串，而值可以是 python所支持的数据类型 ''' def store_person(db): ''' Query user for data and store in the shelf object ''' pid = raw_input('Enter unique ID number: ') person = {} person['name'] = raw_input('Enter name: ') person['age'] = raw_input('Enter age: ') person['phone'] = raw_input('Enter phone number: ') db[pid] = person def lookup_person(db): pid = raw_input("Enter ID number: ") field = raw_input("what would you like to know?(name,age,phone)") field = field.strip().lower() print field.capitalize()+':',db[pid][field] def print_help(): print "The available command are: " print "store :Stores information about a person" print "lookup :look up a person from ID number" print "quit :Save change and exit" print "? :Print this message" def enter_command(): cmd = raw_input("Enter command(? for help): ") cmd = cmd.strip().lower() return cmd def main(): database = shelve.open("D:\\database.dat") try: while True: cmd = enter_command() if cmd == "store": store_person(database) elif cmd == "lookup": lookup_person(database) elif cmd == "?": print print_help() elif cmd =="quit": return finally: database.close() if __name__ == "__main__": main()
14. 将字符串中大写字母转化为小写，小写转化为大写，标点和数字不做变化
#-*- coding:utf-8 -*- str = "WWW.12kuqiao12.COM" # print str.upper() #全部转化为大写 # print str.lower() #全部转化为小写 # print str.title() #把每个单词的第一个字母转化为大写，其余小写 new_str = [] for i in range(len(str)): if str[i].islower(): new_str.append(str[i].upper()) elif str[i].isupper(): new_str.append(str[i].lower()) else: new_str.append(str[i]) print "".join(new_str) # print str1.isdigit() #判断是否是数字 # print str.isalnum() #判断是否是字母和数字的组合 # print str2.isalpha() #判断是否是字母 # print str3.isspace() #判断是否为空格
15.求100以内的质数
#-*- coding:utf-8 -*- num = [] for i in range(2,100): for j in range(2,i/2): if (i%j==0): break else: num.append(i) print num
#-*- coding:utf-8 -*- from math import sqrt def main(): for i in range(101,200): flag = 1 k = int(sqrt(i)) #print k for j in range(2,k+1): if i%j == 0: flag = 0 break if flag == 1: print '%d' %(i), if __name__ =="__main__": main()
16. 1,2,3,4组成数字互不相同的3位数
#-*- coding:utf-8 -*- count = 0 for i in range(1,5): for j in range(1,5): for k in range(1,5): if i != j and i != k and j != k: print i,j,k count +=1 print count
17.某个数，加100是一个完全平方数，再加上168又是一个完全平方数，求这个数；
#-*- coding:utf-8 -*- import math for i in range(0,1000): if i + 100 == int(math.sqrt(i+100))*int(math.sqrt(i+100)) and \ i + 268 == int(math.sqrt(i+268))*int(math.sqrt(i+268)): print i
18. 有一对兔子，从出生后第3个月起每个月都生一对兔子，小兔子长到第三个月后每个月又生一对兔子，假如兔子都不死，问每个月的兔子总数为多少？
#-*- coding:utf-8 -*- def fab(max): n, a, b = 0, 0, 1 while n < max: yield b a, b = b, a + b n = n + 1 for i in fab(6): print i,
19.分解质因数
#-*- coding:utf-8 -*- def main(): n = int(raw_input("Enter a number:")) print n,'=', while(n!=1): for i in range(2,n+1): if (n%i) == 0: #余数9%2 1 n /= i #整除9/2 4 if (n == 1): #余1 print '%d' %(i) else: print '%d*' %(i), break if __name__ == "__main__": main()
上述方法如果输入超过range的范围，则会报错，鉴于此新增了下列方法：
#-*- coding:utf-8 -*- import math number = int(raw_input("Enter a number: ")) list = [] def getChildren(num): isZhishu = True i = 2 square = int(math.sqrt(num)) + 1 while i <= square: if num % i == 0: list.append(i) isZhishu = False getChildren(num / i) i += 1 break i += 1 if isZhishu: list.append(num) getChildren(number) print list
20.字典排序
# -*- coding:utf-8 -*- import operator x = {1:2, 3:4, 4:3, 2:1, 0:0} sorted_x = sorted(x.items(),key=operator.itemgetter(0)) print(sorted_x) new_dict = sorted(x.items(),key=lambda x:x[0]) #x为每次迭代的值 print(new_dict)
