Head_first_python Study Notes (iii)

Use pickle to save, read files

#dump.pyimport pickletry:        with open(‘data.pickle‘,‘wb‘) as data:            pickle.dump([1,2,‘three‘],data)except IOError as err:        print(‘file error:‘ + str(err))except pickle.PickleError as perr:        print(‘pickling error:‘ + str(perr))

#load.pyimport pickletry:        with open(‘data.pickle‘,‘rb‘) as data:                a_list = pickle.load(data)                print a_listexcept IOError as err:        print(‘file error:‘+str(err))except pickle.PickleError as perr:        print(‘pickling error:‘+str(perr))

$ python dump.py $ python load.py [1, 2, ‘three‘]

The fifth chapter deals with data

Read the four score data downloaded from the head first Python website and format the data:

#print_times.pydef print_times(file_name):    time_list = []    try:            with open(file_name+‘.txt‘) as data:                    time_list = data.read().replace(‘-‘,‘:‘).replace(‘.‘,‘:‘)                    time_list =  time_list.strip().split(‘,‘)    except IOError as err:            print(‘file error:‘+str(err))    return time_list

Print test:

• Ctrl+a,ctrl+e shortcut keys available in Mac Terminal Jump to the beginning or end of a line

Derivation list

Convert a list to a different list with some sort of rule

>>>james = print_times.print_times(‘james‘)>>> james[‘2:34‘, ‘3:21‘, ‘2:34‘, ‘2:45‘, ‘3:01‘, ‘2:01‘, ‘2:01‘, ‘3:10‘, ‘2:22‘]>>> jamesLee = [t.replace(‘:‘,‘-‘) for t in james]>>> jamesLee[‘2-34‘, ‘3-21‘, ‘2-34‘, ‘2-45‘, ‘3-01‘, ‘2-01‘, ‘2-01‘, ‘3-10‘, ‘2-22‘]

Sort

• Sort () provides in-place ordering without saving the original order
• Sorted () Copy sort, return a sorted copy
• The default sort method is ascending, descending reverse=true parameter

Using collections to remove list duplicates

>>> james[‘2:01‘, ‘2:01‘, ‘2:22‘, ‘2:34‘, ‘2:34‘, ‘2:45‘, ‘3:01‘, ‘3:10‘, ‘3:21‘]>>> unique = set(james)>>> uniqueset([‘2:45‘, ‘3:21‘, ‘2:01‘, ‘2:22‘, ‘2:34‘, ‘3:10‘, ‘3:01‘])>>> james = list(unique)>>> james[‘2:45‘, ‘3:21‘, ‘2:01‘, ‘2:22‘, ‘2:34‘, ‘3:10‘, ‘3:01‘]

Head_first_python Study Notes (iii)