Array/List from txt file in Python

Question

I was trying to get value from .txt file into array/list in python. Let's say I have this data in user.txt :

  ghost:001
  ghost:002
  ghost:003

So, when I want to output it as :

  'ghost:001','ghost:002','ghost:003'

I use this function

   def readFromFile(filename, use_csv):
        userlist = '' 
        userlist_b = ''
        print ("Fetching users from '%s'"% filename)
        f = open (filename,"r")
        for line in f:
            userlist+=str(line)

        userlist = "','".join(userlist.split("\n"))
        userlist = "'" + userlist + "'" 
        userlist = "(%s)" %userlist

        return userlist

My question is how could I do this: I want to print specific user. Something like

idx = 2
print("User[%s] : %s",%idx, %(array[idx]))

*output:*
User[2] : ghost:003

How do I form the array?

Could anyone help me?

do you want the user by name?

Padraic Cunningham
– Padraic Cunningham

2014-10-31 02:57:16 +00:00
Commented Oct 31, 2014 at 2:57 — Padraic Cunningham
– Padraic Cunningham, Commented Oct 31, 2014 at 2:57

Padraic Cunningham · Accepted Answer · 2014-10-31 03:04:13Z

1

I would store the users in a dict where the keys increment for each user:

d = {}
with open("in.txt") as f:
    user = 1
    for line in f:
       d[user]= line.rstrip()
       user += 1
print(d)
{1: 'ghost:001', 2: 'ghost:002', 3: 'ghost:003'}

If you just want a list of user and to access by index:

with open("in.txt") as f:
   users = f.readlines()

print("User {}".format(users[0]))
User ghost:001

answered Oct 31, 2014 at 3:04

Padraic Cunningham

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Comments

Stefan Gruenwald · Accepted Answer · 2014-10-31 02:57:36Z

0

Look into loading dictionaries. This code should help you.

import json
import pickle

d = { 'field1': 'value1', 'field2': 2, }

json.dump(d,open("testjson.txt","w"))

print json.load(open("testjson.txt","r"))

pickle.dump(d,open("testpickle.txt","w"))

print pickle.load(open("testpickle.txt","r"))

answered Oct 31, 2014 at 2:57

Stefan Gruenwald

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Comments

Gerrat · Accepted Answer · 2014-10-31 03:03:29Z

0

If you want the file (one big string) split out into smaller strings, don't build up a new string, then split it apart again. Just append each line to a list:

def readFromFile(filename, use_csv):
    userlist = []
    print ("Fetching users from '%s'"% filename)
    with open(filename,"r") as f:
        for line in f.read():
            userlist.append(line)
    return userlist

array = readFromFile('somefile', use_csv)
idx = 2
print("User[%s] : %s" % (idx, array[idx]))

answered Oct 31, 2014 at 3:03

Gerrat

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Comments

Phil Cooper · Accepted Answer · 2014-10-31 03:21:57Z

0

Not sure about the User['idx'] part of you desire.

Try to use list comprehensions. Use indexing rather than dictionaries if that's all you need. (I can add a dict version if the seconds part of the line is really the index you are looking up)

# read the file and use strip to remove trailing \n
User = [line.strip() for line in open(filename).readlines()]

# your output
print "User[2] : %s"%User[2]

# commented line is more clear
#print ','.join(User)
# but this use of repr adds the single quotes you showed  
print ','.join(repr(user) for user in User)

output:

User[2] : ghost:003
'ghost:001','ghost:002','ghost:003'

edited Oct 31, 2014 at 3:21

answered Oct 31, 2014 at 3:13

Phil Cooper

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