Beginner question: use function to read text file

[Luke]

I'm pretty stuck at the moment and wondering if anyone can spot the problem.
Trying to create a function that will read a text file into a list and
return that list.

I wrote the following function and saved it as 'fileloader.py'

def fileload(fname):
infile=open(fname)
dates =[]
times=[]
open=[]
high=[]
low=[]
close=[]
vol=[]
count=0
for line in infile:
item=line.split()
dates.append(item[0])
times.append(item[1])
open.append(item[2])
high.append(item[3])
low.append(item[4])
close.append(item[5])
vol.append(item[6])
#print
dates[count],times[count],open[count],high[count],low[count],vol[count]
count=count+1


return dates,times,open,high,low,close


Then I executed the following script (merge contract v1.py):

import fileloader
filename='c:/Python24/test/testdata2.txt'
fileloader.fileload(filename)


I then get the following error messages:

Traceback (most recent call last)
File "C:\Python24\test\merge contract v1.py", in line3, in?
fileloader.fileload(filename)
File ("C:\Python24\text\fileloader.py", in line2, in fileload
infile=open(fname)
UnboundLocalError: local variable 'open' referenced before assignment
Script terminated

Thanks for any help,
Luke

 

[James Stroud]

I'm pretty stuck at the moment and wondering if anyone can spot the problem.
Trying to create a function that will read a text file into a list and
return that list.

I wrote the following function and saved it as 'fileloader.py'

def fileload(fname):
infile=open(fname)
dates =[]
times=[]
open=[]
high=[]
low=[]
close=[]
vol=[]
count=0
for line in infile:
item=line.split()
dates.append(item[0])
times.append(item[1])
open.append(item[2])
high.append(item[3])
low.append(item[4])
close.append(item[5])
vol.append(item[6])
#print
dates[count],times[count],open[count],high[count],low[count],vol[count]
count=count+1


return dates,times,open,high,low,close


Then I executed the following script (merge contract v1.py):

import fileloader
filename='c:/Python24/test/testdata2.txt'
fileloader.fileload(filename)


I then get the following error messages:

Traceback (most recent call last)
File "C:\Python24\test\merge contract v1.py", in line3, in?
fileloader.fileload(filename)
File ("C:\Python24\text\fileloader.py", in line2, in fileload
infile=open(fname)
UnboundLocalError: local variable 'open' referenced before assignment
Script terminated

Thanks for any help,
Luke

def fileload(fname):
infile=open(fname) # <===
dates =[]
times=[]
open=[] # <===

You have assigned open (which, by the way, is a builtin!) in a function
*after* you have referenced it. You have over-ridden the open name with
the assignment, but you have referenced it 'before assignment', as your
error mesage says. This is a favorite trip-up of newer pythong
programmers. Perhaps replace

open=[]

with something like

open_=[]

etc.

James



--
James Stroud
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095

http://www.jamesstroud.com/

 

[Gary Herron]

I'm pretty stuck at the moment and wondering if anyone can spot the problem.
Trying to create a function that will read a text file into a list and
return that list.

I wrote the following function and saved it as 'fileloader.py'

def fileload(fname):
infile=open(fname)
dates =[]
times=[]
open=[]

Here's the problem. You are using the name "open" it two contexts. The
variable named "open" is a local variable, and as such it hides the
builtin function of the same name used to open files. (It does not
matter that the use of "open" as a function precedes the use of "open"
as a variable name. Python is rather strict about this. If you use a
variable in a def, then ANYWHERE in that def, that name refers to the
local variable and hides any uses of the name from enclosing scopes.)
If that last makes sense, good. If not, then just follow this rule:
Choose your variable names to be different than any builtin names -- or
at least different than any of the builtin names you intend to use.

Gary Herron

high=[]
low=[]
close=[]
vol=[]
count=0
for line in infile:
item=line.split()
dates.append(item[0])
times.append(item[1])
open.append(item[2])
high.append(item[3])
low.append(item[4])
close.append(item[5])
vol.append(item[6])
#print
dates[count],times[count],open[count],high[count],low[count],vol[count]
count=count+1


return dates,times,open,high,low,close


Then I executed the following script (merge contract v1.py):

import fileloader
filename='c:/Python24/test/testdata2.txt'
fileloader.fileload(filename)


I then get the following error messages:

Traceback (most recent call last)
File "C:\Python24\test\merge contract v1.py", in line3, in?
fileloader.fileload(filename)
File ("C:\Python24\text\fileloader.py", in line2, in fileload
infile=open(fname)
UnboundLocalError: local variable 'open' referenced before assignment
Script terminated

Thanks for any help,
Luke

 

[Luke]

Thanks to both of you for the help, much appreciated!

Luke