python tips

1. file operation
    fp = open("filename")
    line = fp.readline() //get line
    content = fp.read() //all content of file, that is, read to end
    

2. number
    8/9 = 0
    8/float(9) = 0.88888


3. sort list
    list=['a','e','b','c']
    sorted(list) // sort list
    len(list) //length of list
    for item in list:
        print item //access each item in list


4. sort dict
    dict={'a':2,'e':4,'b':2}
    sorted_keys = sorted(dict.keys())
    for key in sorted_keys:
        print dict[key] //first sort the key, then retrive value for each sorted key

    for k,v in dict.iteritems():
        print k, v // access every key and value

5. string
    import string
    range(start, end, step ) // end will not be contained
    range( 3, 1, -1 ) => 3 2
   
    int('2') //string to int
    str(2) //int to string

    'a'.isdigit() False

6. string format
    %-10s string type, left-pagged, 10 placehode
    print "%-10s %-20s" % ("sss", "tt")

    "sfsd".find('f') == 1
    "aab".replace("b","") == "aa"


7. datetime
    from datetime import datetime

    datetime.max //max datetime
    datetime.min //mindatetime
    datetime.strptime("Sun Oct 25 00:15:34 2009","%a %b %d %H:%M:%S %Y")
    datetime.weekday() //with ()
    datetime.month
    datetime.day
    datetime.hour
    datetime.minute
    datetime.second
    timedelta = datetime1 - datetime2

    all kinds of datetime format can be found:
   
    http://blog.csdn.net/suiyunonghen/archive/2009/03/19/3999986.aspx

8. json parser
    import simplejson

    result = simplejson.loads(content) //retrun dict{} or list[] accoring content,