Trying to figure out the correct loop for processing multiple lines into a dictionary

Question

grocery_stock.txt contains

lemonade 6 1.1

bread 34 1.43

chips 47 3.76

banans 16 0.79

pizza 15 5.0

This is the code i have written for it so far.

    infile=open("grocery_stock.txt", 'r+')
    lines=infile.readlines()
    line=infile.readline()
    none= ' '
    count = 0
    index= 0
    while line !=none:
        line1=infile.readline()

        while line1 in lines:

            line1=line1.split()
            name1=str(line1[:0])
            quant1=(str(line1[:1]))
            price1=[(str(line1[:2]))]
            grocerystock[name1[0]]=(quant1,name1)

            print (grocerystock)

        line2=infile.readline()
        for line2 in line:
            line1=line2.split()
            name1=str(line1[0])
            quant1=(str(line1[1]))
            price1=[(str(line1[2]))]
            grocerystock[name1[1]]=(quant1,name1)
            print (line1[1], line[2],line1[0])
            print (grocerystock)

        line3=infile.readline()
        line4=infile.readline()
        line5=infile.readline()
    infile.close()

    grocerystock={} 

The reason I am doing this is because later in my project im going to have to remove some keys and change some values so i want a function that i can call anywhere into my program when I read a file to convert the data into a dictionary.

My loops might look crazy to you but I was at the point where I was just trying anything that popped in my head.

Also as you can see i havent finished going through line5, I thought it would be better to figure out the correct loop rather than type random loops and see what happens.

Thank you in advance.

Answer 1

Perhaps this would help:

with file('grocery_stock.txt') as f:
    lines = f.readlines()

# filter out empty lines
lines = [line for line in lines if line.strip() != '']

# split all lines
lines = [line.split() for line in lines]

# convert to a dictionary
grocerystock = dict((a, (b, c)) for a, b, c in lines)

# print
for k, v in grocerystock.items():
    print k, v

Answer 2

The only loop you need is the loop to move the data in line-by-line. That can be accomplished with this:

with open("grocery_stock.txt", "r+") as f:
    for line in f: # Changed to be a more elegant solution; no need to use while here.
        # Here we would split (hint) the line of text.
        dict[split_text[0]] = [split_text[1], split_text[2]]

Since it's homework, I encourage you to look into this solution as well as others. I can't just give you the answer, now can I?

Answer 3

Just some hints, since this is HW:

• try to use a context manager to open files, that is a with statement ,
• even if the while is not wrong, I'd prefer a for loop in this case (the number of iterations is fixed - the number of lines) – I sometimes think of while loops as the gateway to the halting problem ...

• try use readlines() , since the number of lines is probably small; or use something like this (which looks just natural):

   for line in f: # do something with line 

Answer 4

When you use open() and you get a file object, you can just iterate on the file object. Like so:

for line in f:
    # do something with the line

I recommend the above rather than calling f.readline() in a loop.

f.readlines() will read the entire file into memory, and build a list of input lines. For very large files, this can cause performance problems. For a small file such as you are using here, it will work, but if you learn the standard Python idiom you can use it for small files or for large ones.