How to save a dictionary to a file

Question

I have problem with changing a dict value and saving the dict to a text file  the format must be same   I only want to change the member phone field   My text file is the following format   memberID member name member email member phone   and I split the text file with   mdict    for line in file      x line split          a x 0      b x 1      c x 2      d x 3      e b     c     d      mdict a  e   When I try change the member phone stored in d  the value has changed not flow by the key    def change mdict b c d e       a input  ID       if a in mdict          d  str input  phone            mdict a  b     c     d     else          print  not     and how to save the dict to a text file with same format

User · Answer

Python has the pickle module just for this kind of thing.

These functions are all that you need for saving and loading almost any object:

def save_obj(obj, name ):
    with open('obj/'+ name + '.pkl', 'wb') as f:
        pickle.dump(obj, f, pickle.HIGHEST_PROTOCOL)

def load_obj(name ):
    with open('obj/' + name + '.pkl', 'rb') as f:
        return pickle.load(f)

These functions assume that you have an obj folder in your current working directory, which will be used to store the objects.

Note that pickle.HIGHEST_PROTOCOL is a binary format, which could not be always convenient, but is good for performance. Protocol 0 is a text format.

In order to save collections of Python there is the shelve module.

User · Answer

We can also use the json module in the case when dictionaries or some other data can be easily mapped to JSON format   import json    Serialize data into file  json dump  data  open   file name json    w         Read data from file  data   json load  open   file name json        This solution brings many benefits  eg works for Python 2 x and Python 3 x in an unchanged form and in addition   data saved in JSON format can be easily transferred between many different platforms or programs  This data are also human-readable

User · Answer

As Pickle has some security concerns and is slow  source   I would go for JSON  as it is fast  built-in  human-readable  and interchangeable  import json data     another dict     a   0   b   1    a list    0  1  2  3     e g  file      data json   with open file   w   as f       json dump data  f   Reading is similar easy  with open file   r   as f      data   json load f   This is similar to this answer  but implements the file handling correctly

User · Answer

I would suggest saving your data using the JSON format instead of pickle format as JSON s files are human-readable which makes your debugging easier since your data is small  JSON files are also used by other programs to read and write data  You can read more about it here  You ll need to install the JSON module  you can do so with pip   pip install json     To save the dictionary into a file  json dump  data  open   myfile json    w        This creates a json file with the name myfile     To read data from file  data   json load  open   myfile json        This reads and stores the myfile json data in a data object

User · Answer

For a dictionary of strings such as the one you re dealing with  it could be done using only Python s built-in text processing capabilities     Note this wouldn t work if the values are something else    with open  members txt   as file      mdict        for line in file          a  b  c  d   line strip   split              mdict a    b         c         d  a   input  ID     if a not in mdict      print  ID    not found  format a   else      b  c  d   mdict a  split          d   input  phone         mdict a    b         c         d    update entry     with open  members txt    w   as file     rewrite file         for id  values in mdict items                file write     join  id    values split           n

User · Answer

file name   open  quot data json quot    quot w quot   json dump test response  file name  file name close    or use context manager  which is better  with open  quot data json quot    quot w quot   as file name      json dump test response  file name

User · Answer

Pickle is probably the best option  but in case anyone wonders how to save and load a dictionary to a file using NumPy   import numpy as np    Save dictionary     hello   world   np save  my file npy   dictionary      Load read dictionary   np load  my file npy  allow pickle  TRUE   item   print read dictionary  hello      displays  world    FYI  NPY file viewer

User · Answer

I haven t timed it but I bet h5 is faster than pickle  the filesize with compression is almost certainly smaller   import deepdish as dd dd io save filename    dict1   dict1   dict2   dict2   compression   blosc   9

User · Answer

Unless you really want to keep the dictionary  I think the best solution is to use the csv Python module to read the file  Then  you get rows of data and you can change member phone or whatever you want   finally  you can use the csv module again to save the file in the same format as you opened it   Code for reading   import csv  with open  my input file txt    r   as f     reader   csv reader f  delimiter         lines   list reader    Code for writing   with open  my output file txt    w   as f     writer   csv writer f  delimiter         writer writerows lines    Of course  you need to adapt your change   function   def change lines       a   input  ID       for line in lines        if line 0     a          d str input  phone            line 3  d         break     else        print  not

User · Answer

I m not sure what your first question is  but if you want to save a dictionary to file you should use the json library  Look up the documentation of the loads and puts functions

User · Answer

Save and load dict to file   def save dict to file dic       f   open  dict txt   w       f write str dic       f close    def load dict from file        f   open  dict txt   r       data f read       f close       return eval data

[python] How to save a dictionary to a file?

Examples related to python

Examples related to file

Examples related to dictionary

Examples related to python-3.x