练习-字符串编码

练习1.1：打印ASCII编码表，包括可见和不可见字符

#coding=utf-8

asciilist = []

chrlist = []

for i in range(255):

    asciilist.append(i)

#a.append(i)为NoneType，返回值为None，布尔判断为false 不能写成a=a.append(i)

print asciilist

for i in asciilist:

    chrlist.append(chr(i))

print chrlist

a 97, z 122, A 65, Z 90, 0 48, 9 57

a-z:    97-122

A-Z:    65-90

0-9:    48-57

练习1.2：打印大写、小写、0-9数字

分析：拼接字符串，在知道ascii的范围的基础上

upper_letters='' #拼接字符串

for i in range(65,91):

upper_letters=upper_letters+chr(i)

for i in range(97,123):

upper_letters=upper_letters+chr(i)

for i in range(48,58):

upper_letters=upper_letters+chr(i)

print upper_letters

练习1.3：26个字母大小写成对打印

#coding=utf-8

#大小写成对出现，并拼接在一个字符串

letters=''

for i in range(26):

    print chr(65+i), chr(65+i+32)

    letters = letters +chr(65+i)+chr(65+i+32)

print letters

练习1.4：输入加解密

#encoding=utf-8

#加解密 规则：a->e b->f c->g w->a x->b y->c z->d

def encode(string):

    str_encode = ""

    for i in string:

        if isinstance(i,str):

            if i>='a' and i<='v':

                str_encode += chr(ord(i)+4)

            elif i>'v' and i<='z':

                str_encode += chr(ord(i)-26+4)

    return str_encode

def decode():

    str_encode = encode(str_original)

    str_decode = ""

    for i in str_encode:

        if isinstance(i,str):

            if i>='e' and i<='z':

                str_decode += chr(ord(i)-4)

            elif i>='a' and i<='d':

                str_decode += chr(ord(i)+26-4)

    return str_decode      

str_original = "abcdwxyz"

print "str_original=",str_original

print "str_encode=",encode(str_original)

print "str_decode=",decode()

练习5：字符的编解码练习

import sys

reload(sys)

sys.setdefaultencoding('utf-8')

print sys.getdefaultencoding()

print type(u'我')

print type(u"我".encode('utf-8'))

print type(u"我".decode('utf-8'))

print "我".encode('utf-8').decode('utf-8')

print "我".encode('utf-8').decode('utf-8') 

# python默认编码是ascii，设定为utf-8，这里“我”是字节字符型，python自动decode为unicode，然后encode成utf-8，再decode成字节字符型

if isinstance(s, basestring):  #判断是否是字符串

    print u”是字符串”