在python解释器中，为什么使用显式“ print”与不使用“ print”之间的结果有所不同？

Question

>>> 'sp\xc4m'
'sp\xc4m'
>>> print('sp\xc4m')
spÄm

( screenshot )

In IDLE,I think that using the function "print" and not using it should be the same. And the book "Learning Python(5th)" supports my opinion.

>>> lumberjack = 'okay'
>>> lumberjack
'okay'

example from book

I am a freshman in python, and my mother language isn't English, so maybe my question and expression are funny, but I keep learning. Thank you for your help.

Answer 1

IDLE prints the repr of a string (or anything else).

>>> print 'sp\xc4m'
sp?m
>>> 'sp\xc4m'
'sp\xc4m'
>>> print repr('sp\xc4m')
'sp\xc4m'
>>> 

Answer 2

The interactive interpreter in IDLE is helpful for debugging. If I wrote:

>>> print s
a       b

What is actually contained in the variable s ? You can check:

>>> s
'a\tb'

Now you can see that it is three characters, a , a tab displayed as the escape sequence \\t , and b . It could have been 'a b' (nine characters with spaces) or `'ab ' (twelve characters with trailing spaces). Both print the same way, but the debugging representation helps determine the exact content via escape codes and quoting the string to visualize the start and end points.

This is called the "representation" of the variable, and is a debug value that can be accessed by the function repr() . IDLE uses it to display variables that weren't explicitly printed.

At the interactive prompt, displaying a variable without print is for debugging. Not using print in a script would display nothing. To force display of the debugging value in a script, use print repr(s) .

Answer 3

The interactive interpreter's auto-print behavior is equivalent to

_ = the_expression_you_typed
if _ is not None:
    print repr(_)

Besides the None thing, this differs from print _ in that print _ would call str instead of repr . Ostensibly, the difference between str and repr is that str is supposed to produce more human-readable output, while repr is supposed to produce something unambiguous, ideally a piece of source code that would produce the object.

Really, though, the main reason the two functions exist is so print "asdf" prints asdf and just typing "asdf" prints "asdf" .