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Thomas Mitchell
Thomas Mitchell

Reputation: 1071

Python split file into list

I'm having trouble with the function below. It seems to split the file fine but then only returns it as one element

Function:

def splitRoute():
  route = []
  for line in open("route.txt","r").readlines():
    line = line.replace("\r","")
    line = line.replace("\n","")
    line = string.split(line, '>')
    route.append(line) 
  return route

Output:

[['B', 'F']]

route.txt contents:

B>F

Is it only returning one element because there is only one line in the file? I have another function that splits another file into a 7x7 list that works fine but is that only reaching all seven elements across because it has 7 lines?

Upvotes: 3

Views: 17396

Answers (2)

Blender
Blender

Reputation: 298048

Why are you replacing newlines? Just split the string:

def splitRoute():
  route = []

  for line in open('route.txt', 'r'):
    route.append(line.strip().split('>')) 

  return route

Upvotes: 3

senderle
senderle

Reputation: 150947

split creates a list. Then you append that list to another (empty) list. So the result is that you get a list inside a list. If you had more lines, you'd get a longer list of lists. Here's a quick breakdown of the code:

def splitRoute():
  route = []

You create an empty list...

  for line in open("route.txt","r").readlines():
    line = line.replace("\r","")
    line = line.replace("\n","")

For every line, you replace \r and \n characters with empty strings. Note that you could do this more easily using line.strip() ('apple\n\r'.strip() -> 'apple'). Also, you should save the file to a filename so you can close it later. Finally, you don't need to use readlines here -- just iterate over the file directly.

    line = string.split(line, '>')

Now you take the string that line refers to, split it into a list, and assign the list to line. Now line looks like this: ['B', 'F']. 

    route.append(line) 
    return route

Now you've appended line to route, and route looks like this: [['B', 'F']].

If your goal is to create a single list, use extend instead of append.

def splitRoute():
  route = []
  f = open('route.txt', 'r')
  for line in f:
    route.extend(line.strip().split('>'))
  f.close()
  return route

Or, using with, and adopting a more readable indentation level:

def splitRoute():
    route = []
    with open('route.txt', 'r') as f:
        for line in f:
            route.extend(line.strip().split('>'))
    return route

Output for a file with two lines ('B>F\nF>X\n'):

>>> splitRoute()
['B', 'F', 'F', 'X']

Upvotes: 1

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