LPTHW - Ex17 - unexpected object type

Python
#1

Hello there, I’m trying to figure out something funky happening when I try to shorten the example code as per study drill. This is the shortened variant:

from sys import argv

script, from_file, to_file = argv

indata = open(from_file).read()

out_file = open(to_file, 'w').write(indata)
print(type(out_file))
print(out_file)

this works fine, but as it turns out, “out_file” is an integer, with the value of len(indata), which surprised me, since I expected a textIOwrapper object:

<class ‘int’>
6

if I rewrite the code to this:

out_file = open(to_file, 'w')
print(type(out_file))
print(out_file)
out_file.write(indata)
print(type(out_file))
print(out_file)

I get, as I’d expected (apart from working code):

<class ‘_io.TextIOWrapper’>
<_io.TextIOWrapper name=‘testto.txt’ mode=‘w’ encoding=‘cp1252’>
<class ‘_io.TextIOWrapper’>
<_io.TextIOWrapper name=‘testto.txt’ mode=‘w’ encoding=‘cp1252’>

could someone please explain what is happening? Thanks in advance.

#2 
out_file = open(to_file, 'w').write(indata)

could be unfolded to

out_file = open(to_file, 'w')
result = out_file.write(indata)

In your shorthand out_file is bound to the return value of write called on the opened file (same as result in my version) and that’s the number of characters written to the file.

#3

Thanks for the explaination!