python: IOError: [Errno 2] No such file or directory when use sublimeREPL

Question

I have put the python file and 'g1.txt' in the same directory. The code runs correctly when I don't use SublimeREPL

def build_graph(file_name):
    new_file = open(file_name, 'r')
    n, m = [int(x) for x in new_file.readline().split()]

    graph = {}
    for line in new_file:
        # u, v, w is the tail, head and the weight of the a edge
        u, v, w = [int(x) for x in line.split()]
        graph[(u, v)] = w

    return n, graph

if __name__ == '__main__':
    print build_graph('g1.txt')

>>> >>> Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 18, in <module>
  File "<string>", line 6, in build_graph
IOError: [Errno 2] No such file or directory: 'g1.txt'

Answer 1

try this:

 import os
 build_graph(os.path.join(os.path.dirname(__file__),"g1.txt"))

it will append the script's directory to g1.txt

Answer 2

Expanding on this answer , SublimeREPL is not necessarily using the same working directory that g1.txt is in. You can either use

import os
build_graph(os.path.join(os.path.dirname(__file__),"g1.txt"))

as previously suggested, or the following will also work:

if __name__ == '__main__':
    import os
    os.chdir(os.path.dirname(__file__))
    print build_graph('g1.txt')

---

Just a minor thing, but you also don't close your file descriptor. You should use the with open() format instead:

def build_graph(file_name):
    with open(file_name, 'r') as new_file:
        n, m = [int(x) for x in new_file.readline().split()]

        graph = {}
        for line in new_file:
            # u, v, w is the tail, head and the weight of the a edge
            u, v, w = [int(x) for x in line.split()]
            graph[(u, v)] = w

    return n, graph

This will automatically close the file descriptor when you're done with it, so you don't have to worry about closing it manually. Leaving files open is generally a bad idea, especially if you're writing to them, as they can be left in an indeterminate state when your program ends.