fqjx.md

lang.py.syntax.print

Print messages to stdout

Synopsis

  print(*[message][, sep=][,end=])

Overview

You can print to stdout in various ways

Arguments

• sep=: Separator for argumets to build the string
• end=: End charactef for the sting
• file=: File object to redirect to
• flush: Avoid buffering of text until a new line character

Definea custom separator and line end

You can use the sep and end arguments to define a separator for your string and a line end. The default is " " and \n respectively. But you can change it to any arbitrary sting

To print different calls to print in the same line, change the end parameter to ''

  print('Mercury', 'Venus', 'Earth', sep=', ', end=', ')
  print('Mars', 'Jupiter', 'Saturn', sep=', ', end=', ')
  print('Uranus', 'Neptune', 'Pluto', sep=', ')

  # Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto

Redirect standard stream

There are three basic standard streams:

• stdin: Represented by 0
• stdout: Represented by 1
• stderr: Represneted by 2

So to write to a file you pass a file object to the file parameter

  with open('file.txt', mode='w') as file_object:
      print('hello world', file=file_object)

Mock a file and redirect to memory

You can mock a file to redirect by writting directly to memory with the io module

  import io

  fake_file = io.StringIO()
  print('hello world', file=fake_file)

  fake_file.getvalue()                      # 'hello world\n'

Print text without buffering

By default print will only print text to the screen after a new line character is encountered.

This is undesirable if you want to print non \n text to the screen sequentialy. To avoid that pass the flsh=True argument to forcefully flush the stream without waiting for a newline character in the buffer

  import time

  num_seconds = 3
  for countdown in reversed(range(num_seconds + 1)):
      if countdown > 0:
          print(countdown, end='...', flush=True)
          time.sleep(1)
      else:
          print('Go!')