Improve company productivity with a Business Account.Sign Up

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 2978
  • Last Modified:

Python, read CSV file into 1D array, or 2D array into 1D array

Hi All

I got the issue to read CSV file into 1D array.

In my csv file, it is only one column.
aaa
bbb
ccc
ddd
eee

After reading CSV file, I got the array key_list:

[['aaa'], ['bbb'], ['ccc']....]

I would like to have 1D array: ['aaa', 'bbb', 'ccc', ......]

How can I read CSV file into 1D array ? or How to make 2D array into 1D array?

Thanks

filename ='test.csv'
    keyreader = csv.reader(open(filename, 'rb'), delimiter= ' ', quotechar='"')
    key_list = []
    for key in keyreader:
        key_list.append(key)
    print key_list

Open in new window

0
mxgong
Asked:
mxgong
  • 3
1 Solution
 
peprCommented:
When iterating through the csv reader object (your line 4 and 5), you get the list representing values from one line of the CSV file.  You have only one element on one line -- so, you get the lists with a single element.  When appending it to another list, you get the list of lists.

This way, your case of processing is somehow special.  Then you can use the .extend() method instead of the .append() at the line 5.
0
 
peprCommented:
Fortgot to mention that the lst.extend() appends all the argument elements to the lst that is being extended -- see http://docs.python.org/tutorial/datastructures.html#more-on-lists and http://docs.python.org/library/stdtypes.html#index-632 (rather difficult to understand it from the standard doc).  See "Dive into Python" by Mark Pilgrim, example 3.10. (http://diveintopython.org/native_data_types/lists.html#d0e5887)

You should always explicitly close the open file. This way your open(filename, 'rb', ...) should be called separately (assigning the object to a variable) and should be closed explicitly after the processing).

You should give the 'key' a kind of better identifier as this one causes confusion later.
0
 
peprCommented:
So, the modified code is:

a.py
import csv

filename ='test.csv'

f = open(filename, 'rb')
reader = csv.reader(f, delimiter= ' ', quotechar='"')
lst = []
for row in reader:
    lst.extend(row)
f.close()
    
print lst

Open in new window


and it prints...

C:\tmp\___python\mxgong\Q_26863285>python a.py
['aaa', 'bbb', 'ccc', 'ddd', 'eee']

Open in new window


The question is what is your final intention.  If the file contains only single elements, no quoting, etc., it may be easier to get the same using a simpler approach:

filename ='test.csv'

f = open(filename)
content = f.read()
f.close()

lst = content.split('\n')
    
print lst

Open in new window


You should also specify bette what do you mean by 1D and 2D array, as there is no standard data type like array in Python.  Arrays are often implemented via lists, the 2D arrays can be implemented via lists of lists.  However, there are packages that implement arrays.
0
 
mxgongAuthor Commented:
Sorry for the late
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

  • 3
Tackle projects and never again get stuck behind a technical roadblock.
Join Now