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自己使用总结Python程序代码片段

时间：2021-07-01 10:21:17 帮助过：123人阅读

用于记录自己写的，或学习期间看到的不错的，小程序，持续更新......
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【例001】计算:1-2+3-4..+199-200值
代码如下:


#encoding=utf-8
#计算 1-2+3-4..+199-200值
#1+3+5+7+...199
#-2-4-6...-200
sum1 = 0
sum2 = 0
for i in range(1,200,2): #计算1+3+5+7...199
sum1 +=i
print sum1


for i in range(-200,0,2): #计算-2+(-4)+(-6)...+(-200)
sum2 +=i
print sum2


print "The total of 1-2+3-4..+199-200 is: ", sum1+sum2

【例002】将两个文件中相同的部分，写到一个文件中

代码如下:


#encoding=utf-8
#Python 2.7.4
#Purpose: 将文件1.txt,2.txt中相同的内容放到3.txt中;
f1 = open("1.txt","r+")
f2 = open("2.txt","r+")
f3 = open("3.txt","w+")


all1 = f1.readlines() #先拿文件1中所有行取出
all2 = f2.readlines() #再拿文件2中所有行取出
f1.close()
f2.close()


for l1 in all1:
for l2 in all2:
if l1.strip()==l2.strip(): #比较行中内容是否一样
f3.write(l2)
else:
continue
else:
pass

print "#"*40
f3.close()

【例003】反向读取文件
假如要读取的test.txt文件内容如下:

代码如下:


Python
Perl
Java
Shell


实现代码:
代码如下:


file1 = file('test.txt','r')
list1 = [] #用一个空列表用于存放每行的内容
while True:
line = file1.readline()
list1.append(line.strip())
if len(line) == 0:
break
for l in list1[::-1]: #反向遍历，然后依次读取出来
print l

file1.close()


输出结果:
代码如下:


Shell
Java
Perl
Python

【例004】 往文件中所有添加指定的前缀

比如文中: print是一个函数

文本文件强制二进制编码
就变成了下面的

代码如下:


01.Python 3.0: #print是一个函数
02.Python 3.0: #文本文件强制二进制编码
#coding = gbk #中文编码

f_r = open('test.txt') #打开要处理文件
f_w = open('file.txt','w') #创建要添加文件

i = 0 #加前缀标志位

while True:
i += 1
line = f_r.readline()
if not line:
break
f_w.write('%02d'%(i) + '.Python 3.0: #' + line)#字符串格式化及拼接技巧

f_r.close() #关闭打开的文件句柄
f_w.close()

【例005】

代码如下:


#coding = gbk
'''''
下面code.txt文件中内容，将
01 CN Chinese
02 IN India
03 HK HongKang
04 JP Japan
05 DE Germany
06 US United States of America
要文件的内容，每一行文件，写到一个文件，且文件名前面两个字段，如
文件名为:01_CN_Chinese.txt
文中内容:01 CN Chinese
知识要点:
1. ''.join 和 split函数
2. 字符的联合
3. with语句,open文件
4. 遍历数组
5. 切片操作
'''
postfix = '.txt' #设置后缀

with open('test.txt') as myfile: #with语句打开文件为myfile
while True: #while循环拿文件读出来
lines = myfile.readlines() #拿所有的行一次性读取到列表中
if not lines: break #没有则中断
for line in lines: #遍历列表
file_out = str('_'.join(line.split()[:])) + postfix #得到01_CN_Chinese.txt文件名
open(file_out,'w').write(line) #write(line),将没行的文件写入新文件中

【例006】

代码如下:


#coding = gbk
'''''
#最终实现下面的过程
foos = [1.0, 2.0, 3.0, 4.0, 5.0]
bars = [100, 200, 300, 400, 500]

1.0 [200, 300, 400, 500]
2.0 [100, 300, 400, 500]
3.0 [100, 200, 400, 500]
4.0 [100, 200, 300, 500]
5.0 [100, 200, 300, 400]
#知识点
1. map函数的理解
2. 关键是切片函数的应用

'''

foos = [1.0, 2.0, 3.0, 4.0, 5.0]
bars = [100, 200, 300, 400, 500]

def func(foo):
index = foos.index(foo) #foo在foos中的索引，拿她取出来
print foo,bars[:][0:index] + bars[:][index+1:]
#该索引同样在bars中相同位置，在切片的时候拿它取出，并拼接这个切片
#大功告成！

print map(func,foos)

【例007】求 6! + 5! + 4! + 3! + 2! + 1!

代码如下:


def factorial(n):
return reduce(lambda x,y: x* y, range(1,n+1))#求6!

print reduce(lambda x,y: x + y, [factorial(i) for i in range(1,6)]) #求6! + 5! + 4! + 3! + 2! + 1!

【例008】 根据输入打印文件

代码如下:


import sys

helpinfo= '''''\
This program prints files to the standard output.
Any number of files can be specified.
Options include:
--[version|VERSION|V|v]: Prints the version number
--[help |HELP |H|h]: Display the help
'''

def readfile(filename):
try:
f = open(filename)
while True:
line = f.readline()
if not line:
break
print line,
except:
print 'some error here'

if len(sys.argv) < 2:
print 'No action is needed!'
sys.exit()

if sys.argv[1].startswith('--'):
option = sys.argv[1][2:]
if option in ['version','v','V','VERSION']:
print 'Version 1.0'
elif option in ['h','H','help','HELP']:
print helpinfo
else:
print 'Unknown option.'
sys.exit()

else:
for filename in sys.argv[1:]:
readfile(filename)

【例009】函数中args的用法

代码如下:


def powersum(power,*args):
'''''Print each argument's power'''
total = 0
for item in args:
total += pow(item,power)
return total

print powersum(2,3,4) # (3**2) + (4**2)
print powersum(2,10) # 10**2
print powersum(2) # 0**2

【例010】匿名函数作为返回值

代码如下:


def repeater(n):
print n
return lambda s: s*n

twice = repeater(2)

print twice('Hello')
print twice(5)


【例011】备份程序
代码如下:


#!/usr/bin/env python

import os,time
source = ['/home/test/C','/home/test/shell'] #源文件目录
target_dir = '/home/test/python' #目标文件目录

today = target_dir + time.strftime('%Y%m%d') #
now = time.strftime('%H%M%S')

if not os.path.exists(today): #判断目录是否存在
os.mkdir(today) #不存在的话则新建
print 'Successfully created directory', today

target = today + os.sep + now + '.zip' #target文件格式
zip_cmd = "zip -qr '%s' %s" % (target, ' '.join(source)) #-q:安静模式 -r递归模式
#等价于 zip -qr /home/test/python20141202/142151.zip /home/test/C /home/test/shell
if os.system(zip_cmd) == 0: #判断命令是否成功执行，成功执行，返回0
print 'Successful back to:', target
else: #失败的话，打印信息
print 'Backup FAILED.'

加comment的版本

代码如下:


#!/usr/bin/env python

import os,time

source = ['/home/test/C','/home/test/shell']
target_dir = '/home/test/python'

today = target_dir + time.strftime('%Y%m%d')
now = time.strftime('%H%M%S')

comment = raw_input('Enter comments here-->') #要输入的comment
if len(comment) == 0: #如果没有comment
target = today + os.sep + now + '.zip' #按照上面的操作执行
else:
target = today + os.sep + now + '_' + comment.replace(' ','_') + '.zip'
#如果有comment,

if not os.path.exists(today):
os.mkdir(today)
print 'The backup directory created!', today

zip_command = "zip -qr '%s' %s" % (target, ' '.join(source))

if os.system(zip_command) == 0:
print 'Scuccessful backup to', target
else:
print 'The backup FAILED'

输出结果 ：

代码如下:


# python backup_ver4.py
Enter comments here-->add new example
The backup directory created! /home/test/python20141202
Scuccessful backup to /home/test/python20141202/145130_add_new_example.zip

【例012】将二进制数转为10进制数

代码如下:


def func(B):
I = 0
while B:
I = I * 2 + (ord(B[0])-ord('0'))
B = B[1:]
return I

b = raw_input('Enter binary here:')

print func(b)


【例013】将列表中排除重复项并将重复的项找出
代码如下:


def find_duplicate(lst):
tmp = [] #临时变量，存放排除后的列表
for item in lst:
if not item in tmp: #将不在tmp变量找出
tmp.append(item)
else:
print 'The duplicate item is:', item
print 'After remove the duplicate item:',
return tmp

if __name__=='__main__':
test = input("Enter List here:") #input技巧
print find_duplicate(test)
>>>
Enter List here:[2,1,4,2]
The duplicate item is: 2
After remove the duplicate item: [2, 1, 4]

【例014】用Python中列表中append()，pop()函数实现简单的堆栈方法:后进先出

代码如下:


l = []
l.append(1)
l.append(2)
l.append(3)
print l
print l.pop()
print l.pop()
print l.pop()



【例015】对列表中的单词按首字母排序
代码如下:


>>> words = ['apple','bat','bar','book','atom']
>>> tmp = {} #建个空字典
>>> for word in words:
letter = word[0] #作为字典中的键
if letter not in tmp: #判断首字母是否存在于字典
tmp[letter] = [word] #注意要添加[],很关键
else:
tmp[letter].append(word) #如果键已经存在，值列表添加


>>> tmp
{'a': ['apple', 'atom'], 'b': ['bat', 'bar', 'book']}

【例016】对文件进行整理（除空格、TAB键、除#!&?等键），假如文本文件全为人名，并让首字母大写

代码如下:


john black
Jerry!
&alice
TOm#
south carolina###
mr smith?


代码及输出结果如下:
代码如下:


import re

def clean(strings):
result = []
for value in strings:
value = value.strip()
value = re.sub('[#!&?]','',value)
value = value.title()
result.append(value)
return result

with open('data.txt','a+') as myfile:
lines = myfile.readlines()
for line in clean(lines):
print line
>>>
John Black
Jerry
Alice
Tom
South Carolina
Mr Smith

【例017】用while循环来判断某个数是否是质数

代码如下:


y = input('Enter a integer Here:')

x = y / 2

while x > 1:
if y % x == 0:
print y, 'has factor', x
break
x -= 1

else:
print y, 'is prime'


【例018】用while实现搜索某个字符串的功能
代码如下:


names = ['Tom','Alice','Wendy','Jerry','Bob','Smith']

while names:
if names[0] == 'Jerry':
print 'Hi,', names[0]
break
names = names[1:]

else:
print 'Not Found!'

【例019】对嵌套的序列进行处理

代码如下:


>>> T = ((1,2),(3,4),(5,6))
>>> for (a,b) in T:
... print a+100, b+200
...
101 202
103 204
105 206


【例020】用for循环实现查找
代码如下:


source = ['sting',(3,4),100,0.1,[1,2]]
tests = [(3,4),3.14]

for t in tests: #先是遍历小循环
for s in source: #再遍历外层循环
if s == t:
print t, 'Found it! '
break
else: #else语句的位置非常关键，
print t, 'Not Found!'

等价于下面这种方式

代码如下:


source = ['sting',(3,4),100,0.1,[1,2]]
tests = [(3,4),100,3.14]

for t in tests:
if t in source:
print t, 'Found it.'
else:
print t, 'Not found.'

【例021】用for循环来收集两个序列中相同的部分

代码如下:


seq1 = 'spam'
seq2 = 'suck'

res = []
for s1 in seq1:
if s1 in seq2:
res.append(s1)

print res

【例022】隔个取出字符串

代码如下:


S = 'abcdefghijklmn'

for i in range(0,len(S),2):
print S[i],

#或者
print S[::2]

【例023】两个列表，列表中每个元素加100，然后与L1中对应元素相乘，形成列表，再对列表求和

代码如下:


L1 = [1,2,3,4]
L2 = [5,6,7,8] #L2每个元素加一百,105,106,107
#(5+100)*1 + (6+100)*2 + (100+7)*3 + (100+8)*4
# 合计: 1070
L3 = [x+100 for x in L2]
L4 = []

for (x,y) in zip(L1,L3):
L4.append(x*y)

print sum(L4)

#或者用下面精简方式，只是刚看到有点头痛!
print sum([x*y for x,y in [T for T in zip(L1,[x+100 for x in L2])]])

【例024】对列表进行，合并，去重，取交集等操作

代码如下:


def func(seq1, seq2=None, opra=None):
res = []
if opra == '-':
for item1 in seq1:
if item1 not in seq2:
res.append(item1)

elif opra == '&':
for item1 in seq1:
if item1 in seq2:
res.append(item1)

elif opra == '|':
tmp = seq1[:]
for item1 in seq2:
if item1 not in seq1:
tmp.append(item1)
return tmp

elif opra == '^':

for i in seq1:
if i not in seq2:
res.append(i)
for i in seq2:
if i not in seq1:
res.append(i)
return res

else:
print 'Need list as input!'

return res

L1 = [1,2,3,4]
L2 = [3,4,5,6]

print '[L1 - L2]:',func(L1,L2,'-')
print '[L1 & L2]:',func(L1,L2,'&')
print '[L1 | L2]:',func(L1,L2,'|')
print '[L1 ^ L2]:',func(L1,L2,'^')


def list_remove(seq):
res = []
for i in seq:
if i not in res:
res.append(i)
return res

L1 = [3,1,2,3,8]
print list_remove(L1)


def find_duplicate(seq):
res = []
for i in range(len(seq)):
if seq.count(seq[i]) >= 2:
print 'Found %s'% seq[i], 'The index is:', i
res.append(seq[i])
return res

L1 = [3,1,2,3,8]
print find_duplicate(L1)

结果如下:

代码如下:


>>>
[L1 - L2]: [1, 2]
[L1 & L2]: [3, 4]
[L1 | L2]: [1, 2, 3, 4, 5, 6]
[L1 ^ L2]: [1, 2, 5, 6]
[3, 1, 2, 8]
Found 3 The index is: 0
Found 3 The index is: 3
[3, 3]

【例025】通过函数改变全局变量的三种方式

代码如下:


var = 99

def local():
var = 0

def glob1():
global var
var += 1

def glob2():
var = 0
import Learn
Learn.var += 1

def glob3():
var = 0
import sys
glob = sys.modules['Learn']
glob.var += 1

def test():
print var
local();glob1();glob2();glob3()
print var

【例026】求range(10)中每个元素的立方

代码如下:


def func():
res = []
for i in range(10):
res.append(lambda x, i=i: i ** x) #i=i这是关键，否则i默认记忆最后一个值:9
return res

>>> res = func()
>>> for i in range(10):
res[i](3)
0
1
8
27
64
125
216
343
512
729

【例027】求最小值

代码如下:


def min1(*args):
mini = args[0]
for arg in args[1:]:
if arg < mini:
mini = arg
return mini

def min2(first,*rest):
mini = first
for arg in rest:
if arg < first:
mini = arg
return mini

def min3(*args):
res = list(args)
res.sort()
return res[0]

print min1('c','a','b')
print min2(3,1,4)
print min3(1,'a',78,'c')
def func(test, *args):
res = args[0]
for arg in args[1:]:
if test(arg, res):
res = arg
return res

def lessthan(x, y): return x < y
def morethan(x, y): return x > y

print func(lessthan, 4,3,1,2,9)
print func(morethan, 4,3,1,2,9)

【例028】求多个集合的交集及合集

代码如下:


def intersect(*args):
res = []
for x in args[0]:
for other in args[1:]:
if x not in other:
break
else:
res.append(x)
return set(res) #去除重复的部分

print intersect('SPAM','SCAM','SLAM')

def union(*args):
res = []
for seq in args:
for item in seq:
if not item in res:
res.append(item)
return res

print union('SA','SB','SC')
def intersect(*args):
res = []
for x in args[0]:
for other in args[1:]:
if x not in other:
break
else:
res.append(x)
#为了交互['S','S','A','A','M','M']
tmp = []
[tmp.append(i) for i in res if i not in tmp]
return tmp

print intersect('SCAM','SPAM','SLAM')

【例029】字典的拷贝及添加

代码如下:


def copyDict(old):
new = {}
for key in old:
new[key] = old[key]
return new

def addDict(d1,d2):
new = {}
for key in d1.keys():
new[key] = d1[key]
for key in d2:
new[key] = d2[key]
return new

【例030】求质数

代码如下:


def isPrime(y):
if y < 1:
print y, 'not prime'
else:
x = y // 2
while x>1:
if y % x == 0:
print y, 'has factor', x
break
x -= 1
else:
print y, 'is prime!'

【例031】比较多个值的大小

代码如下:


def min_max(func,*args):
res = args[0]
for arg in args[1:]:
if func(arg,res):
res = arg
return res

def min_func(x,y): return x < y
def max_func(x,y): return x > y

if __name__=='__main__':
print "The min value is:", min_max(min_func,4,3,2,1,7,6,9)
print "The max value is:", min_max(max_func,4,3,2,1,7,6,9)

# 输出结果:
>>>
The min value is: 1
The max value is: 9

【例032】写一个小函数实现内置函数dir的功能

代码如下:


#Filename: mydir.py

tag = 1

def listing(module):
if tag:
print '-'*30
print 'name:', module.__name__,'file:', module.__file__
print '-'*30

count = 0
for attr in module.__dict__.keys():
if attr[0:2] == '__':
print '%02d) %s' % (count, attr)
else:
print getattr(module,attr)
count = count + 1

if tag:
print '-'*30
print module.__name__, 'has %d names.' % count
print '-'*30

if __name__=='__main__':
import mydir
listing(mydir)

【例033】求分数平均值

代码如下:


'''''Filename: grades.txt 求该文件中第二列的平均值
Jerry 78
Alice 45
Wendy 96
Tom 56
Bob 85
'''

temp = []
for line in open('grades.txt'):
a = line.strip().split()
if a:
temp.append(a[1])

#['78', '45', '96', '56', '85']
total = 0
for i in temp:
total += int(i)

print 'The total grade is:', total, 'The average is:', total/len(tmp)

【例034】一个实际类的例子

代码如下:


class GenericDisplay:
def gatherAttrs(self):
attrs = '\n'
for key in self.__dict__:
attrs += '\t%s=%s\n' % (key, self.__dict__[key])
return attrs
def __str__(self):
return '<%s: %s>' % (self.__class__.__name__, self.gatherAttrs())

class Person(GenericDisplay):
def __init__(self, name, age):
self.name = name
self.age = age
def lastName(self):
return self.name.split()[-1]
def birthDay(self):
self.age += 1

class Employee(Person):
def __init__(self, name, age, job=None, pay=0):
Person.__init__(self, name, age)
self.job = job
self.pay = pay
def birthDay(self):
self.age += 2
def giveRaise(self, percent):
self.pay *= (1.0 + percent)

if __name__ == '__main__':
bob = Person('Bob Smith', 40)
print bob
print bob.lastName()
bob.birthDay()
print bob

sue = Employee('Sue Jones', 44, job='dev', pay=100000)
print sue
print sue.lastName
sue.birthDay()
sue.giveRaise(.10)
print sue

【例035】根据给定的年月日以数字方式打印出日期(February 27th, 2015)

代码如下:


# coding = UTF-8
#根据给定的年月日以数字形式打印出日期
months = [
'January' ,
'February',
'March' ,
'April' ,
'May' ,
'June' ,
'July' ,
'August' ,
'September',
'October' ,
'November' ,
'December'
]
#以1~31的数字作为结尾的列表
endings = ['st','nd','rd'] + 17 * ['th'] + \
['st','nd','rd'] + 07 * ['th'] + \
['st']

year = raw_input('Year: ')
month = raw_input('Month(1-12): ')
day = raw_input('Day(1-31): ')

month_number = int(month)
day_number = int(day)
#月份和天数减1来获得正确的索引
month_name = months[month_number - 1]
ordinal = day + endings[day_number - 1]

print month_name + ' ' + ordinal + ', ' + year

#输出结果
>>>
Year: 2015
Month(1-12): 2
Day(1-31): 27
February 27th, 2015

【例036】在居中的盒子里打印一条语句

代码如下:


sentence = raw_input("Sentence: ")

screen_width = 80
text_width = len(sentence)
box_width = text_width + 6
left_margin = (screen_width - box_width) // 2

print
print ' '*left_margin + '+' + '-'*(box_width-4) + '+'
print ' '*left_margin + '| ' + ' '*(text_width) +' |'
print ' '*left_margin + '| ' + sentence +' |'
print ' '*left_margin + '| ' + ' '*(text_width) +' |'
print ' '*left_margin + '+' + '-'*(box_width-4) + '+'
print

#输出结果
>>>
Sentence: Welcome To Beijing!

+---------------------+
| |
| Welcome To Beijing! |
| |
+---------------------+

【例037】简单小数据库验证

代码如下:


database = [
['Bob', '1234'],
['Tom', '2345'],
['Foo', '1478']
]
usr = raw_input('Enter username: ')
pwd = raw_input('Enter password: ')

if [usr, pwd] in database:
print 'Access Granted!'
else:
print 'Access Deny!'

【例038】使用给定的宽度打印格式化后的价格列表

代码如下:


width = input('Please enter width: ')

price_width = 10
item_width = width - price_width

header_format = '%-*s%*s'
format = '%-*s%*.2f'

print '=' * width

print header_format % (item_width, 'Item', price_width, 'Price')

print '-' * width

print format % (item_width, 'Apples', price_width, 0.4)
print format % (item_width, 'Sweets', price_width, 0.5)
print format % (item_width, 'Pepper', price_width, 12.94)
print format % (item_width, 'Tender', price_width, 42)

print '-' * width

输出格式:

代码如下:


>>>
Please enter width: 30
==============================
Item Price
------------------------------
Apples 0.40
Sweets 0.50
Pepper 12.94
Tender 42.00
------------------------------

【例039】遍历两个对应列表

代码如下:


names = ['Alice', 'Bob' , 'Cherry', 'David']
numbers = ['0000' , '1111', '2222' , '3333' ]

for index,name in enumerate(names):
print '%-7s=> %s' % (name, numbers[index])

#输出结果
>>>
Alice => 0000
Bob => 1111
Cherry => 2222
David => 3333

当然也可以采用如下通常的做法:

代码如下:


names = ['Alice','Bob', 'John', 'Fred']
ages = [27, 23, 31, 29]
for i in range(len(ages)):
print names[i],' is ', ages[i], ' years old!'

#输出结果:
>>>
Alice is 27 years old!
Bob is 23 years old!
John is 31 years old!
Fred is 29 years old!

【例040】对存储在小字典中数据进行查询

代码如下:


peoples = {
'Alice':{
'phone' : '0948',
'address' : 'aaaa'
},
'Wendy':{
'phone' : '4562',
'address' : 'bbbb'
},
'David':{
'phone' : '4562',
'address' : 'bbbb'
}
}
#字典使用人名作为键。每个人用另外一个字典来表示，其键'phone'和'addr'分别表示他们的电话号码和地址


labels = {
'phone' : 'phone number',
'address' : 'address'
}
#针对电话号码和地址使用描述性标签，会在打印输出时用到。
key = ''
name = raw_input('Name: ')


if name in peoples:
request = raw_input('Enter (p) or (a): ')
if request == 'p':
key = 'phone'
elif request == 'a':
key = 'address'
else:
print 'Please input p(phone) an a(address)!'
print "%s's %s is %s" % (name, labels[key],peoples[name][key])

else:
print 'Not Found!'

或者使用字典的get()方法，更好些。完整代码如下:

代码如下:


#字典使用人名作为键。每个人用另外一个字典来表示，其键'phone'和'addr'分别表示他们的电话号码和地址
peoples = {
'Alice':{
'phone' : '0948',
'address' : 'aaaa'
},
'Wendy':{
'phone' : '4562',
'address' : 'bbbb'
},
'David':{
'phone' : '4562',
'address' : 'bbbb'
}
}


#针对电话号码和地址使用描述性标签，会在打印输出时用到。
labels = {
'phone' : 'phone number',
'addr' : 'address'
}

name = raw_input('Name: ')
#查找电话号码还是地址?
request = raw_input('Phone number (p) or address (a)? ')

#查找正确的键
key = request #如果请求即不是p也不是a
if request == 'p': key = 'phone'
if request == 'a': key = 'addr'

#使用get()函数提供默认值
person = peoples.get(name,{})
label = labels.get(key, key)
result = person.get(key, 'not available')

print "%s's %s is %s." % (name, label, result)

【例041】字典格式化字符串例子

代码如下:


template='''''

%(title)s


%(text)s

'''

data = {'title':'My Home Page','text':'Welcome to my home page!'}
print template % data

#输出结果:
>>>


My Home Page


Welcome to my home page!


【例042】需找100以内的最大平方数

代码如下:


from math import sqrt
#从100开始往下找，找到即停止，最大为: 81
for n in range(99, 0, -1):
root = sqrt(n)
if root == int(root):
print n
break

【例043】用while/True, break控制输入

代码如下:


while True: #一直进行下去，除非break
word = raw_input('Please Enter a word: ')
if not word: break #输入为空的话，中断循环
print 'The word was: ' + word


【例044】将两个列表中首字母相同的提取出来
代码如下:


#将两个列表中首字母相同的罗列在一起
girls = ['alice', 'bernice', 'clarice']
boys = ['chris', 'arnold', 'bob']
#列表推导:
print [b+'+'+g for b in boys for g in girls if b[0] == g[0]]
#输出结果:
>>>
['chris+clarice', 'arnold+alice', 'bob+bernice']

【例045】斐波那契数列求指定数字的列表

代码如下:


def fibs(x):
fibs = [0, 1] # 初始值
for i in range(x):
# fibs[-2]+fibs[-1]：最新一个值是前面两个值之和
# 并用append方法将其添加在后面
fibs.append(fibs[-2]+fibs[-1])
print fibs

if __name__=='__main__':
num = input('How many Fibonacci numbers do you want? ')
fibs(num)

或者用普通方法实现:

代码如下:


>>> def fib(max):
n, a, b = 0, 0, 1
tmp_list = []
while n < max:
tmp_list.append(a)
a, b = b, a+b
n += 1
return tmp_list

>>> fib(8)
[0, 1, 1, 2, 3, 5, 8, 13]

【例046】写一个自定义列表类，让它支持尽可能多的支持操作符号

代码如下:


class MyList:
def __init__(self, start):
self.wrapped = [] # Make sure it's a list here
for x in start:
self.wrapped.append(x)
def __add__(self, other):
return MyList(self.wrapped + other)
def __mul__(self, time):
return MyList(self.wrapped * time)
def __getitem__(self, offset):
return self.wrapped[offset]
def __len__(self):
return len(self.wrapped)
def __getslice__(self, low, high):
return MyList(self.wrapped[low:high])
def append(self, node):
self.wrapped.append(node)
def __getattr__(self, name): # Other members: sort/reverse/etc
return getattr(self.wrapped, name)
def __repr__(self):
return repr(self.wrapped)

if __name__ == '__main__':
x = MyList('spam')
print x
print x

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