我的词典程序需要帮助

Question

def createdictionary():
    mydictionary = dict()
    mydictionary['Computer']='Computer is an electronic machine.'
    mydictionary['RAM']='Random Access Memory'
    return mydictionary

def insert(dictionary):
    print("Enter the keyword you want to insert in the dictionary: ")
    key=input()
    print("Enter its meaning")
    meaning=input()
    dictionary[key]=meaning
    f = open('dict_bckup.txt','a')
    f.write(key)
    f.write('=')
    f.write(meaning)
    f.write(';\n')
    f.close()
    print("Do you want to insert again? y/n")
    ans=input()
    if ( ans == 'y' or ans=='Y' ):
        insert(dictionary)

def display(dictionary):
    print("The contents of the dictionary are : ")
    f = open('dict_bckup.txt','r')
    print(f.read())
    f.close()

def update(dictionary):
    print("Enter the word whose meaning you want to update")
    key=input()
    #i want to edit the meaning of the key in the text file
    f = open('dict_bckup.txt','w')
    if key in dictionary:
        print(dictionary[key])
        print("Enter its new meaning: ")
        new=input()
        dictionary[key]=new
    else:
        print("Word not found! ")
    print("Do you want to update again? y/n")
    ans=input()
    if (ans=='y' or ans=='Y'):
        update(dictionary)

def search(dictionary):
    print("Enter the word you want to search: " )
    word=input()
    if word in dictionary:
        print(dictionary[word])

else:
    print("Word not found! ")
print("Do you want to search again? y/n")
ans=input()
if(ans=='y' or ans=='Y'):
    search(dictionary)


def delete(dictionary):
    print("Enter the word you want to delete: ")
    word=input()
    if word in dictionary:
        del dictionary[word]
        print(dictionary)
    else:
        print("Word not found!")

    print("Do you want to delete again? y/n ")
    ans=input()
    if ( ans == 'y' or ans == 'Y' ):
        delete(dictionary)

def sort(dictionary):
    for key in sorted(dictionary):
        print(" %s: %s "%(key,(dictionary[key])))


def main():
    dictionary=createdictionary()
    while True:

        print("""             Menu
            1)Insert
            2)Delete
            3)Display Whole Dictionary
            4)Search
            5)Update Meaning
            6)Sort
            7)Exit
          Enter the number to select the coressponding field """)

        ch=int(input())

        if(ch==1):
            insert(dictionary)

        if(ch==2):
            delete(dictionary)

        if(ch==3):
            display(dictionary)

        if(ch==4):
            search(dictionary)

        if(ch==5):
            update(dictionary)

        if(ch==6):
            sort(dictionary)

        if(ch==7):                                        
            break


main()

I am new to python. I have been trying for days to get this. But still no solution found. The thing is initially i made a simple dictionary program which stores words and their meanings. Then i thought i should store the words permanently. I have somewhat tried to store the words in a text file and displaying it. But i am not getting how to search the word in the text file. And suppose i find the word and i want to update its meaning. So how should i do it. Cause if i use the 'w' to rewrite it the whole text file and it will get rewritten. And also how should i delete it. I know the way I have inserted the word in the text in the file is also wrong. Please help me with this.

Answer 1

As @Vaibhav Desai mentionned, you can write the entire dictionary at regular intervals. Consider for instance the pickle module which writes serialized objects:

import pickle

class MyDict(object):
    def __init__(self, f, **kwargs):
        self.f = f
        try:
            # Try to read saved dictionary
            with open(self.f, 'rb') as p:
                self.d = pickle.load(p)
        except:
            # Failure: recreating
            self.d = {}
        self.update(kwargs)

    def _writeback(self):
        "Write the entire dictionary to the disk"
        with open(self.f, 'wb') as p:
            pickle.dump(p, self.d)

    def update(self, d):
        self.d.update(d)
        self._writeback()

    def __setitem__(self, key, value):
        self.d[key] = value
        self._writeback()

    def __delitem__(self, key):
        del self.d[key]
        self._writeback()

    ...

This will rewrite the entire dictionary to the disk every time you make a modification, which might make sense for some cases, but is probably not the most efficient. You can also make a more clever mechanism which calls _writeback at regular intervals, or require it to be called explicitly.

As others have suggested, if you require a lot of writes to the dictionary, you would be better off using the sqlite3 module , to have a SQL table as your dictionary:

import sqlite3

class MyDict(object):
    def __init__(self, f, **kwargs):
        self.f = f
        try:
            with sqlite3.connect(self.f) as conn:
                conn.execute("CREATE TABLE dict (key text, value text)")
        except:
            # Table already exists
            pass

    def __setitem__(self, key, value):
        with sqlite3.connect(self.f) as conn:
            conn.execute('INSERT INTO dict VALUES (?, ?)', str(key), str(value))

    def __delitem__(self, key):
        with sqlite3.connect(self.f) as conn:
            conn.execute('DELETE FROM dict WHERE key=?', str(key))

    def __getitem__(self, key):
        with sqlite3.connect(self.f) as conn:
            key, value = conn.execute('SELECT key, value FROM dict WHERE key=?', str(key))
            return value

    ...

This is just an example, you can for instance maintain the connection open and require it to be closed explicitly, or queue your queries... But it should give you a rough idea of how you can persist data to the disk.

In general, the Data Persistence section of the Python documentation can help you to find the most appropriated module for your problem.

Answer 2

You are right, storing these values in a simple text file is a bad idea. If you want to update one word, you have to rewrite the whole file. And for searching a single word you might end up with searching every word in the file.

There are some data structures specially designed for dictionary (for example, Trie tree), but assuming your dictionary is not really really big, you can use a sqlite database. Python has sqlite3 library. Check the documentation for more info.

Answer 3

First of all, writing to the disk every time an update or insert happens to the dictionary is a very bad idea - your program simply uses up too much I/O. Hence, an easier way to do it would be to store the key-value pairs within a dictionary and save it to the disk either when the program quits or at some regular time interval.

Also, in case you are not keen on storing data on the disk in a human readable form (such as aa plain text file); you can consider using the built-in pickle module as shown here to save the data to a well defined disk location. Hence during program start-up you can read from this well-defined location and "un-pickle" the data back into a dictionary object. This way you can work solely with the dictionary object and even operations such as finding an item or deleting an item can be done easily.Please refer to the below script that solves your requirement. I have used the pickle module to persist to the file, you may want to dump it to a text file and read from it as a separate exercise. Also, I have not introduced my function with the suffix 2 for eg insert2 so that you can compare your function with mine and understand the differences:

One another thing - There was bug in your program; you should use raw_input() to read in user input and not input()

import pickle
import os

def createdictionary():
    mydictionary = dict()
    mydictionary['Computer']='Computer is an electronic machine.'
    mydictionary['RAM']='Random Access Memory'
    return mydictionary

#create a dictionary from a dump file if one exists. Else create a new one in memory.    
def createdictionary2():

    if os.path.exists('dict.p'):
        mydictionary = pickle.load(open('dict.p', 'rb'))
        return mydictionary

    mydictionary = dict()
    mydictionary['Computer']='Computer is an electronic machine.'
    mydictionary['RAM']='Random Access Memory'
    return mydictionary

def insert(dictionary):
    print("Enter the keyword you want to insert in the dictionary: ")
    key=raw_input()
    print("Enter its meaning")
    meaning=raw_input()
    dictionary[key]=meaning
    f = open('dict_bckup.txt','a')
    f.write(key)
    f.write('=')
    f.write(meaning)
    f.write(';\n')
    f.close()
    print("Do you want to insert again? y/n")
    ans=raw_input()
    if ( ans == 'y' or ans=='Y' ):
        insert(dictionary)

#custom method that simply updates the in-memory dictionary
def insert2(dictionary):
    print("Enter the keyword you want to insert in the dictionary: ")
    key=raw_input()
    print("Enter its meaning")
    meaning=raw_input()
    dictionary[key]=meaning

    print("Do you want to insert again? y/n")
    ans=raw_input()
    if ( ans == 'y' or ans=='Y' ):
        insert(dictionary)



def display(dictionary):
    print("The contents of the dictionary are : ")
    f = open('dict_bckup.txt','r')
    print(f.read())
    f.close()

#custom display function - display the in-mmeory dictionary
def display2(dictionary):
    print("The contents of the dictionary are : ")
    for key in dictionary.keys():
        print key + '=' + dictionary[key] 

def update(dictionary):
    print("Enter the word whose meaning you want to update")
    key=input()
    #i want to edit the meaning of the key in the text file
    f = open('dict_bckup.txt','w')
    if key in dictionary:
        print(dictionary[key])
        print("Enter its new meaning: ")
        new=raw_input()
        dictionary[key]=new
    else:
        print("Word not found! ")
    print("Do you want to update again? y/n")
    ans=input()
    if (ans=='y' or ans=='Y'):
        update(dictionary)

#custom method that performs update of an in-memory dictionary        
def update2(dictionary):
    print("Enter the word whose meaning you want to update")
    key=input()
    #i want to edit the meaning of the key in the text file

    if key in dictionary:
        print(dictionary[key])
        print("Enter its new meaning: ")
        new=raw_input()
        dictionary[key]=new
    else:
        print("Word not found! ")
    print("Do you want to update again? y/n")
    ans=raw_input()
    if (ans=='y' or ans=='Y'):
        update(dictionary)

def search(dictionary):
    print("Enter the word you want to search: " )
    word=raw_input()
    if word in dictionary:
        print(dictionary[word])

    else:
        print("Word not found! ")
    print("Do you want to search again? y/n")
    ans=raw_input()
    if(ans=='y' or ans=='Y'):
        search(dictionary)


def delete(dictionary):
    print("Enter the word you want to delete: ")
    word=raw_input()
    if word in dictionary:
        del dictionary[word]
        print(dictionary)
    else:
        print("Word not found!")

    print("Do you want to delete again? y/n ")
    ans=raw_input()
    if ( ans == 'y' or ans == 'Y' ):
        delete(dictionary)

def sort(dictionary):
    for key in sorted(dictionary):
        print(" %s: %s "%(key,(dictionary[key])))

#this method will save the contents of the in-memory dictionary to a pickle file
#of course in case the data has to be saved to a simple text file, then we can do so too
def save(dictionary):
    #open the dictionary in 'w' mode, truncate if it already exists
    f = open('dict.p', 'wb')
    pickle.dump(dictionary, f)




def main():
    dictionary=createdictionary2() #call createdictionary2 instead of creatediction
    while True:

        print("""             Menu
            1)Insert
            2)Delete
            3)Display Whole Dictionary
            4)Search
            5)Update Meaning
            6)Sort
            7)Exit
          Enter the number to select the coressponding field """)

        ch=int(input())

        if(ch==1):
            insert2(dictionary)  #call insert2 instead of insert

        if(ch==2):
            delete(dictionary)

        if(ch==3):
            display2(dictionary) #call display2 instead of display

        if(ch==4):
            search(dictionary)

        if(ch==5):
            update2(dictionary) #call update2 instead of update

        if(ch==6):
            sort(dictionary)

        if(ch==7):                                        
            #save the dictionary before exit
            save(dictionary);
            break


main()