How can I change any data type into a string in Python?
10 Answers
myvariable = 4
mystring = str(myvariable) # '4'
also, alternatively try repr:
mystring = repr(myvariable) # '4'
This is called "conversion" in python, and is quite common.
4 Comments
Abgan
I wouldn't use repr(myvariable) - it often returns information about class type, memory address etc. It's more useful for debugging. Use str(myvariable) for conversion to string and unicode(variable) for conversion to unicode.
Robsdedude
What about unicode? Something like
str(u'ä') will not work. However repr(u'ä') will work.
fredless
what about None and False?
Charlie Parker
does every class/type in python always allows
str to be called on it without error?str is meant to produce a string representation of the object's data. If you're writing your own class and you want str to work for you, add:
def __str__(self):
return "Some descriptive string"
print str(myObj) will call myObj.__str__().
repr is a similar method, which generally produces information on the class info. For most core library object, repr produces the class name (and sometime some class information) between angle brackets. repr will be used, for example, by just typing your object into your interactions pane, without using print or anything else.
You can define the behavior of repr for your own objects just like you can define the behavior of str:
def __repr__(self):
return "Some descriptive string"
>>> myObj in your interactions pane, or repr(myObj), will result in myObj.__repr__()
4 Comments
abarnert
It's probably true that the majority of core library objects by raw percentage return the
object.__repr__-style angle-bracket representation, but many of the most commonly used ones do not. The rule of thumb for repr is that if it makes sense to return Python code that could be evaluated to produce the same object, do that, just like str, frozenset, and most other builtins do, but if it doesn't, use the angle-bracket form to make sure that what you return can't possibly be mistaken for a human-readable-and-evaluatable-as-source repr.abarnert
(Of course some of the builtins violate that rule of thumb—a
list that includes itself returns something that not only looks like but is evaluable code, which evaluates to the wrong thing—but the core devs have never taken that as license to expand the same behavior into the stdlib.)Charlie Parker
does every class/type in python always allows
str to be called on it without error?
Brian S
@CharlieParker yes;
__str__ is a function inherited from the object class, which is the root for all other classes in Python. docs.python.org/3/reference/datamodel.html#object.__str__I see all answers recommend using str(object). It might fail if your object have more than ascii characters and you will see error like ordinal not in range(128). This was the case for me while I was converting list of string in language other than English
I resolved it by using unicode(object)
2 Comments
dmjalund
in Python 3.0 onward, str(object) does unicode by default
Charlie Parker
does every class/type in python always allows
str to be called on it without error?str(object) will do the trick.
If you want to alter the way object is stringified, define __str__(self) method for object's class. Such method has to return str or unicode object.
4 Comments
Kedar.Aitawdekar
Which method is efficient?
str(any_var) or any_var.__str__()Abgan
@Kedar.Aitawdekar: Even if there is noticeable difference in execution time (which I doubt, but I encourage you to vefiry it using
timeit module), you should use str(any_var) since it's more readable for human and allows to benefit from cases when any_var defines __repr__() but doesn't define __str__().Charlie Parker
does every class/type in python always allows
str to be called on it without error?Abgan
@CharlieParker : Yes,
str() can be called freely on any Python object, including classes, modules, function objects etc. It is possible to implement __str__ on a custom type in a way that would raise an exception, but generally speaking it's possible to make an error in any custom code. ;)Use the str built-in:
x = str(something)
Examples:
>>> str(1)
'1'
>>> str(1.0)
'1.0'
>>> str([])
'[]'
>>> str({})
'{}'
...
From the documentation:
Return a string containing a nicely printable representation of an object. For strings, this returns the string itself. The difference with repr(object) is that str(object) does not always attempt to return a string that is acceptable to eval(); its goal is to return a printable string. If no argument is given, returns the empty string, ''.
1 Comment
Charlie Parker
does every class/type in python always allows
str to be called on it without error?With str(x). However, every data type can define its own string conversion, so this might not be what you want.
1 Comment
jathanism
This is an important yet rare consideration. Good that you mentioned it.
You can use %s like below
>>> "%s" %([])
'[]'
Comments
Just use str - for example:
>>> str([])
'[]'
Comments
Be careful if you really want to "change" the data type. Like in other cases (e.g. changing the iterator in a for loop) this might bring up unexpected behaviour:
>> dct = {1:3, 2:1}
>> len(str(dct))
12
>> print(str(dct))
{1: 31, 2: 0}
>> l = ["all","colours"]
>> len(str(l))
18
Comments
Use formatting:
"%s" % (x)
Example:
x = time.ctime(); str = "%s" % (x); print str
Output: Thu Jan 11 20:40:05 2018
str(var)? is that what you're looking for?strto be called on it without error?