Python - converting multiple lines to one

Question

I have a question concerning some python code that I have written:

def read_graph_from_file(filename):

   txtfile = open(filename, "rU")

   node_memory = 0
   neighbour_list = 0

   for entry in txtfile:
       entry_without_newline = entry.replace('\n',"")
       columns = entry_without_newline.replace(','," ")
       columns = columns.split(" ")
       number_of_columns = len(columns)

       if number_of_columns == 2:
           neighbour_list = columns
           neighbour_list.sort()

           if node_memory == float(neighbour_list[0]):
               y = neighbour_list[1]
               print y

The output I want from this is a list, i.e. [1,4]. Instead I am receiving the characters across multiple lines, i.e:

1

4

I was wondering how I might rectify this?

You're printing y individually, which will result in a new line per iteration. Instead, append to a list first, then print the list at the end. — jayelm
– jayelm, Commented Sep 28, 2014 at 2:07
You can also use print y, to print a space instead of a newline, or accumulate a string to point out, etc. But if you want to print a list, the obvious thing to do is to create a list, as @JesseMu says. — abarnert
– abarnert, Commented Sep 28, 2014 at 2:19

Eugene S · Accepted Answer · 2014-09-28 02:28:55Z

If you want them in a list, you will have to create a list variable and just append your results to it. You should return this list once your function is done.

def read_graph_from_file(filename):

   txtfile = open(filename, "rU")

   node_memory = 0
   neighbour_list = 0

   lst = []

   for entry in txtfile:
       entry_without_newline = entry.replace('\n',"")
       columns = entry_without_newline.replace(','," ")
       columns = columns.split(" ")
       number_of_columns = len(columns)

       if number_of_columns == 2:
           neighbour_list = columns
           neighbour_list.sort()

           if node_memory == float(neighbour_list[0]):
               y = neighbour_list[1]
               lst.append(y)
   return lst

Then if you run your function like this:

print read_graph_from_file(<fileName>)

You will get the desired result:

[1,4]

Alternatively, you can print the resulting list directly at the end of your function. Then you won't have to call the function with print.

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