On Tuesday 16 February 2016 00:05, Veek. M wrote:
> When I do at the interpreter prompt,
> repr( open('/etc/motd', 'rt').read() )
Opening and reading MOTD is a needless distraction from your actual
question. This demonstrates the issue most simply:
# at the interactive interpreter
py> s = "text\n"
py> s # evaluate the string s
'text\n'
py> repr(s)
"'text\\n'"
Evaluating the string `s` in the REPL (Read-Eval-Print Loop) displays the
repr() of the string. Contrast that to using print directly:
py> print s # note the blank line
text
py> print repr(s)
'text\n'
So when you call print on a string, the string is printed in the most
accurate way possible. When you call repr() on a string, it returns a new
string containing the Python representation of a string.
So the string:
text
plus newline (but without the indent) has a representation in Python of:
'text\n'
so repr("text\n") == "'text\n'"
If you call repr() twice, you get this string:
py> print repr(repr("text\n"))
"'text\\n'"
That should look familiar:
py> repr(s)
"'text\\n'"
So when you evaluate a string on its own, the REPL prints the repr() of the
string. So if you evaluate repr(s), you see repr(repr(s)) printed.
> With # 2 # read returns a string that the interpreter displays by
> calling __str__ via print so newlines are converted to \n.
No, that's incorrect. The REPL uses the repr() of the string. We can test
this with a class that makes the difference between __str__ and __repr__
more obvious:
py> class C(object):
... def __repr__(self):
... return "the repr"
... def __str__(self):
... return "the str"
...
py> c = C()
py> print(c)
the str
py> c
the repr
--
Steve
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