I am generating random edges from a graph and printing them, but every time I try to save it to a text file, I end up with errors like `TypeError: expected a character buffer object`. The code is below:

```
import re
import md5
import pickle
import networkx as nx
import itertools
from random import choice

ff=open("testfile.txt","r+")
G=nx.read_gpickle("authorgraph_new.gpickle")
for nodes in G:
    random_edge=choice(G.edges())
    ff=open("testfile.txt","a")
    ff.write(random_edge)

```

I need to save the outputs of random\_edge in a text file preferably in columns, as the value of `random_edge` is in the form `(abcdef, pqrstu)`. I want to put the two in separate column in the same line and the next value in the same columns. I know I can use the `"\n"` to get the outputs to newline but when I used 

```
ff.write(random_edge + "\n")

```

I get an error `TypeError: can only concatenate tuple (not "str") to tuple`.