(python) for some reason file.readline() is only reading every second line

[david2031]

why is this skipping readlines in what it returns? i went through debugger and found it thinks the second line of the txt file is the first and continues to skip every second line.

def get_distances(filename):
    opener = open(filename)
    d = {}
    while file.readline(opener) != '':
        '''converts a file with cities and distances into a dictionary with values
        of distances from one city to other cities and then stores that dictionary
        in a list with values specific to each city
        '''
        #storing the line which has been read in a list
        read = file.readline(opener)
        my_list = read.split(":")
        my_list[1] = my_list[1].split()

        max = len(my_list[1]) - 1
        my_list.append(my_list[1][max])
        my_list[1].pop()

        if max > 1:
            my_list[1] = my_list[1][0] + ' ' + my_list[1][1]
        else:
            my_list[1] = my_list[1][0]
        print my_list
        if d.has_key(my_list[0]):
            d[my_list[0]].append((my_list[1],my_list[2]))
        else:
            d[my_list[0]] = [(my_list[1],my_list[2])]
    return d
print get_distances('cities.txt')

and it returns. i put the print of my_list in there to illustrate how it skips lines.

['New York', 'Washington', '2']
['San Francisco', 'Mexico City', '3']
['Toronto', 'San Francisco', '6']
{'Toronto': [('San Francisco', '6')], 'San Francisco': [('Mexico City', '3')], 'New York': [('Washington', '2')]}

and etc. depending on how many more cities i add to the txt file. any suggestions on how to solve this problem?
my text file is 'cities.txt'

Toronto:New York 3
New York:Washington 2
Washington:San Francisco 5
San Francisco:Mexico City 3
Toronto:Mexico City 7
Toronto:San Francisco 6

[david2031]

i realize i the while statement reads it once everytime the loop goes through thus skipping the line. sorry for waste.

[bvdet]

Instead of using readline(), try iterating on the file object as in:

f = open("filename.txt")
for line in f:
    .... do stuff ...
f.close()

[david2031]

i am just learning python so some obvious things i are not so obvious to me. for that project i ended up making two opens for the same file but as of now i have updated myself on how and when to use for loops. thanks.

[Buzzer159]

I realize the original post is 9 years old (LOL!) but it was the only thing that Google threw up for the problem I encountered when converting a program from csv processing to flat file processing.

I ended up with;
=============== ===============

# Open the file
f = open(inputfile, "r") #
#
# Read the file and process the data
#
for row in f:
row = f.readline() # Read a record
ETC.
=============== =============== =====

Which as the OP notes, results in the program reading record 2,4,6,8 etc

And the same applies if you use 'for x in f' or whatever.

I tried a couple of things then eventually commented out the readline statement completely

=============== =============== ========

# Open the file
f = open(inputfile, "r") #
#
# Read the file and process the data
#
for row in f:
# row = f.readline() # Read a record
ETC.
=============== =============== =====

And it worked! Weird. So there's an implied read somewhere in that for statement ('cos there ain't one in my code!

Hope this helps some fellow traveller :-)