str() vs repr() functions in python 2.7.5
When should i use str() and when should i use repr() ?
Almost always use str()
when creating output for end users.
repr()
is mainly useful for debugging and exploring. For example, if you suspect a string has non printing characters in it, or a float has a small rounding error, repr()
will show you; str()
may not.
repr()
can also be useful for generating literals to paste into your source code. It can also be used for persistence (with ast.literal_eval
or eval
), but this is rarely a good idea--if you want editable persisted values, something like JSON or YAML is much better, and if you don't plan to edit them, use pickle.
2.In which cases i can use either of them ?
Well, you can use them almost anywhere. You shouldn't generally use them except as described above.
3.What can
str()
do whichrepr()
can't ?
Give you output fit for end-user consumption--not always (e.g., str(['spam', 'eggs']) isn't likely to be anything you want to put in a GUI), but more often than repr()
.
4.What can
repr()
do whichstr()
can't
Give you output that's useful for debugging--again, not always (the default for instances of user-created classes is rarely helpful), but whenever possible.
And sometimes give you output that's a valid Python literal or other expression--but you rarely want to rely on that except for interactive exploration.
AnV
Updated on September 22, 2020Comments
-
AnV almost 4 years
what is the difference between
str()
andrepr()
functions in python 2.7.5?Explanation on python.org:
The
str()
function is meant to return representations of values which are fairly human-readable, whilerepr()
is meant to generate representations which can be read by the interpreter (or will force aSyntaxError
if there is no equivalent syntax)But it wasn't clear for me.
some examples:
>>> s = 'Hello, world.' >>> str(s) 'Hello, world.' >>> repr(s) "'Hello, world.'" # repr is giving an extra double quotes >>> str(1.0/7.0) '0.142857142857' >>> repr(1.0/7.0) '0.14285714285714285' # repr is giving value with more precision
so I want to know the following
- When should I use
str()
and when should I userepr()
? - In which cases I can use either of them?
- What can
str()
do whichrepr()
can't? - What can
repr()
do whichstr()
can't?
- When should I use