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I have a text file with columns of data and I need to turn these columns into individual lists or arrays. This is what I have so far

f = open('data.txt', 'r')
temp = []
for row in f.readlines():
    Data = row.split()
    temp.append(float(Data[0]))

When I run this I get IndexError: list index out of range.

Snippet of the data below:

16  0.2000  
17  0.3000  
18  0.4000  
20  0.5000  
21  0.6000  
22  0.7000
24  0.8000  
25  0.9000
26  1.000

I need the first column, if possible to look like this: Data = [16, 17, 18, 20, 21, 22, 24, 25, 26]

Ooker
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user1762768
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7 Answers7

6

You are getting an empty list Data=[] if you read an empty row. You try to get the first element from the list using Data[0],but because it's an empty list it doesn't have an element at position 0, so you get an IndexError. 

Data=''.split()

Data[0]
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-686-0792b03cbbdf> in <module>()
----> 1 Data[0]

IndexError: list index out of range

This will print out the Data if IndexError occours - you can see yourself that it prints an empty list:

f=open('file','r')
temp = []
for row in f.readlines():
    Data = row.split()
    try:
        temp.append(float(Data[0]))
    except IndexError:
        print Data

You can use the with statement to open the file, that automatically closes the file after being processed. Also you can loop over the file itself, without using readlines().

with open(file,'r') as f:        
     for row in f:
         Data = row.split()
         try:
            print Data[0]
         except IndexError:
            print 'You have an empty row'

EDIT: You are better of using the csv module:

import csv
with open('file.csv', 'rb') as f:
    reader = csv.reader(f, delimiter=' ')
    print [row[0] for row in reader if len(row)]
>>> 
['16', '17', '18', '20', '21', '22', '24', '25', '26']
root
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  • Thanks very much for your feedback and suggestions. Is there a way that I can then get the Data into a list form like this: Data = [0, 1, etc]? – user1762768 Oct 21 '12 at 09:34
  • I'm just trying to get the data into a list because I need to then use it to perform a linear interpolation. If I use the last method you suggested, (using 'with') will that give me a list that I can then use later in my interpolation? The 0,1, etc were just examples of the data values being imported – user1762768 Oct 21 '12 at 09:45
  • if you want to use interpolation take a look at the pandas library (it can import the data dirctly from csv), here's an interpolation example using pandas as an answer to a previous question http://stackoverflow.com/questions/12982792/interpolate-number-sequence/12983037#12983037 – root Oct 21 '12 at 10:25
  • Ok just one more question, will this work if I want to do the same for other columns from the data? – user1762768 Oct 21 '12 at 10:25
  • yes it will. just change row[0] to row[1], if you have rows that have the first value and not the second you may need to add if len(row)>1 to avoid index error. – root Oct 21 '12 at 10:28
  • I tried the code and rather than giving me the values just from the first column its giving me the values from all columns? – user1762768 Oct 21 '12 at 11:21
  • is the data still separated by a space? It looks like a delimeter issue. – root Oct 21 '12 at 11:26
  • Do you mean after I've run it? If so, then no its not – user1762768 Oct 21 '12 at 11:35
  • No in the file. delimiter='' breaks the rows by whitspace, if it is something else that separates the values, it wont work. – root Oct 21 '12 at 11:38
  • Oh ok, yeah I just checked and there is no spaces. I will put spaces and see if it works – user1762768 Oct 21 '12 at 11:41
2

use with for filehandlers.

with open('path/to/file', 'r') as f:
    for line in f:
        # code.

you index error comes from trying to access Data at the [0] location. which simply means your line was empty.

you should run a quick check before parsing the line...

if len(Data):
    #code
else:
    #empty line?
Inbar Rose
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0
f = open('data.txt', 'r')
temp = []
for row in f.readlines():
    items = row.split(',')
    temp.append(unicode(items[0]))

I hope that it solves your problem.

okan kilic
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def cal(num_list):
    x = 1;
    z = 0;
    while True:
        list1 = list(str(x))
        list2 = [int(a) for a in list1]

        for i in range(len(list2)):
            for j in range(10):
                if(list2.count(j) > num_list[list2[i]]):
                    z = 1;
                    break;
        if(z == 1):   
            save(x);
            break;      
        x = x + 1;
Nerdroid
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user4730171
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#matrix A to B
def show():
    global string_final,list_2,tot
    index=matrix_1.index(num)  # finding index of num

    length=n
    j=(index)%length # the column positon
    i=index/length # the row position

    list_1=[]
    for a in range(length):
        lis=[]
        for b in range(length):

            lis.append(matrix_1.pop(0)) #pop the first element and append the list

        list_1.append(lis)

    tot=0
    list_2=[]

    for a in range(i+1):
        for b in range(j+1):
            tot=tot+list_1[a][b] # add the numbers
            list_2.append(list_1[a][b]) #append to list
            if(b!=length):
                list_2.append(" ")  #append space
        list_2.append("\n")
    string_final="".join([str(a) for a in list_2])  #list to string


    print "matrix B\n",string_final,"\nx: ",str(num),"\nn: ",str(n)+"\ntotal: "+str(tot) # print the result
Nathan Tuggy
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user4816019
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  • #mat A to b def saveFile(): file=open("matrix2.txt","w") file.write("matrixB\n"+string_final+"\nx: "+str(num)+"\nn: "+str(n)+"\ntotal: "+str(tot)) file.close(); x=1 while x==1: getInput() if(n<=0 or n>=20): #check for the n print "enter correct n" break if(len(matrix_1)!=n*n or len(set(matrix_1))!=len(matrix_1)): # check the input is ok or not print "wrong input" break if(set([99>a>9 for a in matrix_1])!={True}):# check the value of n print "enter suitable number" break show() saveFile() x=x+1; – user4816019 Apr 22 '15 at 00:36
  • Comments destroy code formatting, especially in whitespace-significant languages. Please [edit] your answer to include the additional code. – Nathan Tuggy Apr 22 '15 at 01:30
0
#matrix add zero
def get():
    global b_no
    num_list=[];
    file=open("matrix.txt","r");
    for i in file:
        b_no=0
        if(len(i.split())==1): #check length is 1 or not
            n=int(i)#string to int
        else:
            temp=i.split();
            if(len(temp)!=n):
                b_no+=1
                break
            temp=[0]+[int(a) for a in temp]+[0] #add zero at first and last
            num_list.append(temp);

    zero_list=[]

    for i in range(n+2):
        zero_list.append(0)         #append zero
    num_list.insert(0,zero_list)
    num_list.insert(n+1,zero_list)
    return num_list,n;
Ken Y-N
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user4816019
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  • #mat Add zero# def cal(): list1=[]; for row in range(1,n+1): for col in range(1,n+1): tot=0; count=0; for m in range(-1,2): for p in range(-1,2): if(num_list[row+m][col+p]==0): count=count+1; tot=tot+num_list[row+m][col+p]; if(count!=0): tot=tot/(9-count); else: tot=tot/9 list1.append(str(tot)+" "); list1.append("\n"); print "".join([str(a) for a in list1]) – user4816019 Apr 22 '15 at 00:51
  • x=1; while x==1: num_list,n=get(); if(n>20 or n<3): print "n should between 3 and 20" break if(b_no!=0): print "enter correctly" break cal() x=x+1; – user4816019 Apr 22 '15 at 00:54
0

I would avoid using Data[0] or row[0], instead, I would use ''.join(Data) or ''.join(row) to avoid empty list (list index out of range error).

kevin
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