Python Dynamic Execution

Question

I have a list of dictionary items stored in variable List_dicts, and I have to write a selected list of items from the above list into a file. given below my python function:

def write_items(List_dicts,key_list):
  #List_dicts contains the list if dicts
  #key_list contains the key separated by comma
  k_list=key_list.split(',')
  write_string=''
  for i in k_list:
    write_string=write_string+"item['"+i+"'],"
  f=open('log.txt','w')
  for item in List_dicts:
    f.write(write_string[0:len(write_string)-1]) #this should write item['key1'],item['key2'],item['key3']..,item['keyn'] not the value of string 'write_string'
  f.close()

Is this possible in anyways? I was inspired from SQL dynamic execute quires.

use csv with dictwriter

thkang
– thkang

2013-04-23 16:46:09 +00:00
Commented Apr 23, 2013 at 16:46 — thkang
– thkang, Commented Apr 23, 2013 at 16:46

thkang · Accepted Answer · 2013-04-23 16:57:06Z

3

edit : judging from your code, your function doesn't appear to be writing anything related to the contents of dicts. you are writing write_string[0:len(write_string)-1] to your file for each dict you got(which is just a copy of your write_string without last trailing comma) and the write_string has nothing to with items in your dict, it's just selected keys from the key_list.

there is a python module, csv, with a class called DictWriter, which is suitable for your job.

import csv

def write_dicts(dicts, keys, filename):

   with open(filename, 'w') as csvfile:
       writer = csv.DictWriter(csvfile, keys, extrasaction='ignore')
       for d in dicts:
           writer.writerow(d)

edited Apr 23, 2013 at 16:57

answered Apr 23, 2013 at 16:48

thkang

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Paco · Accepted Answer · 2013-04-23 16:47:59Z

0

I'm not sure I understand the question, but if I do, here's what you should be using: http://docs.python.org/2/library/pickle.html

Basically it allows you to store python objects in files. Here's a quick example you should have a look at: http://wiki.python.org/moin/UsingPickle

answered Apr 23, 2013 at 16:47

Paco

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Martijn Pieters · Accepted Answer · 2013-04-23 16:58:03Z

0

Apart from being better off using the csv module, what you did wrong was that you overcomplicated things.

You already have a list of keys to write, so just loop directly over those keys:

def write_items(List_dicts, key_list):
    k_list = key_list.split(',')
    with open('log.txt','w') as f:
        for item in List_dicts:
          for key in k_list:
              f.write(item[key])

answered Apr 23, 2013 at 16:58

Martijn Pieters

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