python字典的小程序

#coding=utf-8
#古老的rot13加密法
def rot13Encode(str):
    arr = [];
    str = str.lower();
    for i in range(len(str)):
        if str[i]>='a' and str[i]<='z':
            ordNum = ord(str[i]);
            if ordNum>ord('m'):  #ord将字符转化为数字
                arr.append(chr(ordNum-13));  #chr将数字转化为对应的字符
            else:
                arr.append(chr(ordNum+13));
        else:
            arr.append(str[i]);
    return ''.join(arr);
    
if __name__=='__main__':
    #将两个字典合并在一起的方法
    a = {'key1':'value1','key2':'value2'};
    b = {'key1':'value3','key3':'value4'};
    a.update(b); #update()函数把字典b的键/值对更新到a里
    print a;
    
    #按照字典的顺序显示一个字典的键
    c = {'a':1,'c':2,'ac':3,'b':4};
    print sorted(c.keys());
    
    #按照字典的顺序显示一个字典的键和值
    for key in sorted(c.keys()):
        print key,c[key];
        
    #按照已经排好序的字典的值，显示字典的键和值
    for value in sorted(c.values()):
        for key in c.keys():
            if c[key] == value:
                print key,value;
                break;
    
    #rot13加密法
    str = rot13Encode('Hello world!');
    print str.capitalize();