Newbie question: Tuples and reading csv files

[Gryff]

Hi

Its been 20 years since I programmed, so I'm stepping back in via
Python. However I'm beating my brains on tuples/lists (what I used to
know as arrays). I've fooled around with small code snippets and tried
a few things, but I can't figure out how to grab elements of
tuples ...

For example, I'm reading in a small csv file like this:

import csv

csvfile = open("example.csv")

#sniff the dialect
dialect = csv.Sniffer().sniff(csvfile.read(1024))
csvfile.seek(0)

# get file in using reader method

mylist=[]
reader = csv.reader(csvfile, dialect)

# grab the lines into a reader and pass to mylist

for row in reader:

mylist.append(row)

# now print something out to prove this worked

print mylist[:3]

and the output I get is:

['Date', 'Open', 'High', 'Low', 'Close', 'Volume', 'Adj Close']
['2010-03-05', '224.20', '230.70', '223.80', '228.30', '5051500',
'228.30']
['2010-03-04', '223.00', '228.50', '220.50', '224.50', '4040500',
'224.50']

So far so good but not useful. My "mylist" has all the data in there,
but I can only figure out how to get each line out!?!
-> I want to get access to the individual items in each line. In my
bad old days I'd have used an array and grabbed "mylist
[row,item]" ...job done. Try as I like and after *lots* of reading
around, I can't figure out whether:

a) I'm missing something...really...simple
b) "You can't do that" (and I should just use numpy and arrays?)
c) errrr....

Like I said, basic/newbie question from a programmer who spent 20
years away from it.

Cheers


Gareth

 

[Steve Howell]

Hi

Its been 20 years since I programmed, so I'm stepping back in via
Python. However I'm beating my brains on tuples/lists (what I used to
know as arrays). I've fooled around with small code snippets and tried
a few things, but I can't figure out how to grab elements of
tuples ...

For example, I'm reading in a small csv file like this:

import csv

csvfile = open("example.csv")

#sniff the dialect
dialect = csv.Sniffer().sniff(csvfile.read(1024))
csvfile.seek(0)

# get file in using reader method

mylist=[]
reader = csv.reader(csvfile, dialect)

# grab the lines into a reader and pass to mylist

for row in reader:

    mylist.append(row)

# now print something out to prove this worked

print mylist[:3]

and the output I get is:

['Date', 'Open', 'High', 'Low', 'Close', 'Volume', 'Adj Close']
['2010-03-05', '224.20', '230.70', '223.80', '228.30', '5051500',
'228.30']
['2010-03-04', '223.00', '228.50', '220.50', '224.50', '4040500',
'224.50']

So far so good but not useful. My "mylist" has all the data in there,
but I can only figure out how to get each line out!?!
-> I want to get access to the individual items in each line. In my
bad old days I'd have used an array and grabbed "mylist
[row,item]" ...job done.

You are not too far:

mylist[row][item]

If you try that and still get an error (unlikely), be sure to post the
exact code you tried and any error messages.

 

[Kushal Kumaran]

Hi

Its been 20 years since I programmed, so I'm stepping back in via
Python. However I'm beating my brains on tuples/lists (what I used to
know as arrays). I've fooled around with small code snippets and tried
a few things, but I can't figure out how to grab elements of
tuples ...

For example, I'm reading in a small csv file like this:

import csv

csvfile = open("example.csv")

#sniff the dialect
dialect = csv.Sniffer().sniff(csvfile.read(1024))
csvfile.seek(0)

# get file in using reader method

mylist=[]
reader = csv.reader(csvfile, dialect)

# grab the lines into a reader and pass to mylist

for row in reader:

   mylist.append(row)

# now print something out to prove this worked

print mylist[:3]

and the output I get is:

['Date', 'Open', 'High', 'Low', 'Close', 'Volume', 'Adj Close']
['2010-03-05', '224.20', '230.70', '223.80', '228.30', '5051500',
'228.30']
['2010-03-04', '223.00', '228.50', '220.50', '224.50', '4040500',
'224.50']

So far so good but not useful. My "mylist" has all the data in there,
but I can only figure out how to get each line out!?!
-> I want to get access to the individual items in each line. In my
bad old days I'd have used an array and grabbed "mylist
[row,item]" ...job done. Try as I like and after *lots* of reading
around, I can't figure out whether:

mylist is a list of lists. mylist[0] gives you the first list (the
row with the column headings, in your case). You can get the first
item in that list by mylist[0][0].

 

[Gryff]

*tada!* *enlightenment*

Thanks - I figured it was something simple....