Is there a Python equivalent / pseudo-equivalent to java's OutputStream or PrintWriter?
I want to be able to have a handle that represents either a stream like stdout/sterr, or a file, or something else (a pipe or a socket or a dummy sink) and abstract away what kind of thing it is, so I can just send output to it.
How can I do this?
"Abstracting away what type it is" happens automatically in Python - it's called 'duck typing'. Just pass any file-like object to the function, and have it use the interface of file-like objects.
FWIW, the standard input/output/error streams are represented by stdin, stdout and stderr in the sys module. To get file-like objects that read and write strings, use the StringIO module.
you just need an object that implements the methods that files, pipes, streams, etc... also implement. for instance, i use this class sometimes when i want to detach my python program and i want to redirect sys.stderr/sys.stdout:
class Log(object):
"""used for logging for background process"""
def __init__(self, f):
self.f = f
def write(self, s):
self.f.write(s)
self.f.flush()
sys.stdout = sys.stderr = Log(open('/tmp/daemonlog', 'a+'))
If you're interested just in abstracting away from the type of output you are using, just use the file parameter of built-in print function.
For example, you can use the following to print to standard output:
import sys
print("Hello world",file=sys.stdout)
Or use the following to print into a file instead:
output_file = open("output.txt","w")
print("Hello world",file=output_file)
# ...
output_file.close()
Here's documentation of the built in function: https://docs.python.org/3/library/functions.html#print
