Headers with Python List

Question

Python newbie. I have csv data the looks like the following:

Record  Name    Cur     e12mo   e24mo   e48mo   state
3928    Joes    2000    200     400     0       CA,GA
1       Toms    19       1      2       0       AR,KS
1747    Mine    60       5      10      0       AR,CT
5023    Yours   5        12     24      0       FL
7041    Theirs  10       2      4       0       FL

Am entering code from tutorial as follows:

import numpy as np
import csv as csv

readdata = csv.reader(open('c:\MyData\BYLCsv.csv'))
for row in readdata:
    print(row)
data = []  
for row in readdata:
    data.append(row)
for row in data:
    print(row)
Header = data[0]
data.pop(0)

Code bombs on the "Header = data[0]" statement. Everything runs up to there.

Please post the name of the error and the full traceback helpfully provided to you by Python. — Two-Bit Alchemist
– Two-Bit Alchemist, Commented Mar 8, 2015 at 21:02

Daniel · Accepted Answer · 2015-03-08 21:06:50Z

2

In your first loop, you read the whole file, the file pointer is not reset afterwards:

import numpy as np
import csv as csv
with open('c:\MyData\BYLCsv.csv') as data:
    readdata = csv.reader(data)
    header = next(readdata)
    data = list(readdata)
print(header)
for row in data:
    print(row)

answered Mar 8, 2015 at 21:06

Daniel

42.9k4 gold badges57 silver badges82 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

jpl458 Over a year ago

Thanks, this works well. Had to read up on 'with' . I am assuming the the statement 'data = list(readdata)" takes the data from readdata and creates the list. I can read any row now with something like "print(data[230])" .

Yuri Malheiros · Accepted Answer · 2015-03-08 22:09:52Z

1

Try to put everything in the same for:

import numpy as np
import csv as csv

readdata = csv.reader(open('c:\MyData\BYLCsv.csv'))
data = []  

for row in readdata:
    print(row)
    data.append(row)

for row in data:
    print(row)

Header = data[0]
data.pop(0)

You are trying to iterate twice over the readdata iterator, and it can be consumed just once

edited Mar 8, 2015 at 22:09

answered Mar 8, 2015 at 21:03

Yuri Malheiros

1,41011 silver badges16 bronze badges

3 Comments

user1902824 Over a year ago

Yuri is correct. The reasoning is that csv.reader opened the file for reading, and since you went through and printed everything, you are now at the end of the file. There is probably a way to seek back to the beginning of the file, or you can do as Yuri suggested and do your debug printing and appending in the same loop.

jpl458 Over a year ago

Don't know how to put everything in the same, very new to this. I used Daniels example and it worked great. Would like to see an example of what you mean. Is Daniels example the best way to do this type of thing( the most Pythonic)?

Yuri Malheiros Over a year ago

Yes, he did well. But what I tried to show to you is that your code failed because you did two fors like that: "for row in readdata", and just the first one ran ok, because readdata uses an iterator, and you can consume an iterator just once. Thus, after the first for, the data in readdata can't be used. So, if you use just one "for row in readdata" you'll be ok.

Collectives™ on Stack Overflow

Headers with Python List

2 Answers 2

1 Comment

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related