If I run the following program (using Python 3.8.3 on a Windows 10 laptop):
import sys, time
for i in range(1,11):
sys.stdout.write('\r%d' % i)
time.sleep(1)
As intended, it displays '1', replacing it at 1-second intervals with
'2', '3' ... '10'.
Now run the same code inside the REPL:
Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:20:19) [MSC v.1925 32
bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys, time
>>> for i in range(1,11):
... sys.stdout.write('\r%d' % i)
... time.sleep(1)
...
12
22
32
42
52
62
72
82
92
103
>>>
It appears that the requested characters are output, *followed by* the
number of characters output
(which is the value returned by sys.stdout.write) and a newline.
Surely this is not the intended behaviour.
sys.stderr behaves the same as sys.stdout.
Python 2 does NOT exhibit this behaviour:
Python 2.7.18 (v2.7.18:8d21aa21f2, Apr 20 2020, 13:19:08) [MSC v.1500 32
bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys, time
>>> for i in range(1,11):
... sys.stdout.write('\r%d' % i)
... time.sleep(1)
...
10>>>
# displays '1', '2' ... '10' as intended.
Best wishes
Rob Cliffe
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