Question

The pagesubs() function reads a text file into a string,then uses Python’s format() to substitute for arguments given in the subs parameter.

Here are examples:
My attempt was as follows:

def pagesubs(N,*subs):
    assert type(N)==str
    F= open(N,'r')
    return F.format(subs)

I get an error that F is type(file) but I thought the open() reads a text file into a string. Any help is greatly appreciated

EDIT: Example

 pagesubs('index.html', 'December', 18, 2012)

  This will return the content of the file index.html, but 
  with "December" substituted for {0}, and 18 substituted
  for {1}, and 2012 substituted for {2}.  

Answer 1

You need to call the read() function on your file in order to get it’s content into a string. Try the following code instead:

def pagesubs(N, *subs):
    assert type(N)==str
    with open(N,'r') as F:
        content = F.read()
    return content.format(subs)