Python 3.2 Idle vs terminal

问题:

In python 3.2 under OSX, if I'll run "type(sys.stdin)" under Idle I get a strange answer as shown below

>>> type(sys.stdin)
<class 'idlelib.rpc.RPCProxy'>
>>> 

But if I'll reun the same command under terminal, I get:

>>> import sys
>>> type(sys.stdin)
<class '_io.TextIOWrapper'>
>>> 

I understand this is because I'm running it under IDLE. but is this not misleading?

I was trying to run the following commands in IDLE and spent hours trying to understand as to why this is not working. (I'm still a python noob)

>>> w = sys.stdin.readlines()
Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    w = sys.stdin.readlines()
AttributeError: readlines

But just discovered that I works fine under terminal.

>>> w = sys.stdin.readlines()
wow
ww
wewew
>>> 
>>> w
['wow\n', 'ww\n', 'wewew\n']
>>> 

Is this a bug?

回答1:

This is a filed Python bug:

http://bugs.python.org/issue9290

The fact that in IDLE sys.stdin is a idlelib.rpc.RPCProxy results in programs having different behavior in IDLE and in Command Line mode.

I noticed that when grading many students exercises in IDLE. Things like:

sys.stdin.readlines()

just don´t exists in IDLE, but are fully operational in Command Line mode.

In Command Line mode, sys.stdin is a file.

This is expected, as the manual (27.1) says that sys.stdin (and stdout and stderrr) are "File objects corresponding to the interpreter’s standard input"

There are also other "quirks".

I fell that is really strange that stdin has different behavior for the same program.

---

Note that this is probably not fixed because readlines is not normally useful. Instead, you can just iterate over the file objects itself:

for line in sys.stdin:
    ...