What is a Python equivalent of PHP's var_dump()? [duplicate]

Question

When debugging in PHP, I frequently find it useful to simply stick a var_dump() in my code to show me what a variable is, what its value is, and the same for anything that it contains.

What is a good Python equivalent for this?

I found this looking for the PHP equivalent for pythons repr. Thanks. — Danny Staple
– Danny Staple, Commented Apr 30, 2012 at 15:47
the duplicate question @hop mentions (and the highest voted answer) was much more useful for me — cwd
– cwd, Commented Aug 24, 2012 at 18:46
If you find yourself using this function a lot you may want to consider using a good remote debugger with breakpoints. It maybe hard to understand at first, but it will save you time in the future and once you know how to do it, you will never go back. I know eclipse has a good one and so does Komodo. docs.activestate.com/komodo/8.0/… — styks
– styks, Commented Mar 12, 2014 at 13:10
since this thread is closed, see this answer that uses jsonpickle serialization: stackoverflow.com/a/35804583/1081043 — wisbucky
– wisbucky, Commented Mar 4, 2016 at 19:34

Gustavo Straube · Accepted Answer · 2015-10-30 16:45:27Z

350

I think the best equivalent to PHP's var_dump($foo, $bar) is combine print with vars:

print vars(foo),vars(bar)

edited Oct 30, 2015 at 16:45

Gustavo Straube

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answered May 22, 2010 at 17:21

Jan

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6 Comments

Kin Over a year ago

Same here, only thing that worked as I expected (like var_dump)

Ken Over a year ago

Looks like for vars to work, the variable must have a dictionary info, otherwise you get "TypeError: vars() argument must have __ dict __ attribute".

dsummersl Over a year ago

This did it for me - but I like the pprint too. Here is a hybrid: pprint.pprint(vars(foo)).

GetFree Over a year ago

-1, this works only for some types of variables, not all of them. Consider instead pprint or repr

Armstrongest Over a year ago

Note: For python3 you'll need to use parens like print( vars(foo) )

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Nikita · Accepted Answer · 2017-03-24 22:08:09Z

332

To display a value nicely, you can use the pprint module. The easiest way to dump all variables with it is to do

from pprint import pprint pprint(globals()) pprint(locals())

If you are running in CGI, a useful debugging feature is the cgitb module, which displays the value of local variables as part of the traceback.

edited Mar 24, 2017 at 22:08

Nikita

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answered Dec 21, 2008 at 0:59

Martin v. Löwis

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5 Comments

holms Over a year ago

what about showing the type of var? like Null/None, String, Object..

JSmyth Over a year ago

What about pprint() on enumerate objects, permutations, etc.?

Elijah Lynn Over a year ago

This was helpful. I am a Python noob but what seemed to help my case was using .__dict__, e.g. pprint(object.__dict__).

akahunahi Over a year ago

object.__dict__ outputs all the properties of the object

Rain Over a year ago

var_dump in PHP is not just about "displaying a value nicely" 😁

Peter Mortensen · Accepted Answer · 2014-05-09 05:10:40Z

77

The closest thing to PHP's var_dump() is pprint() with the getmembers() function in the built-in inspect module:

from inspect import getmembers from pprint import pprint pprint(getmembers(yourObj))

edited May 9, 2014 at 5:10

Peter Mortensen

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answered May 22, 2012 at 10:58

Hai Phaikawl

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1 Comment

Hola Soy Edu Feliz Navidad Over a year ago

This way is much more better of good.

hanshenrik · Accepted Answer · 2022-05-09 09:06:28Z

I wrote a very light-weight alternative to PHP's var_dump for using in Python and made it open source later.

GitHub: https://github.com/sha256/python-var-dump

You can simply install it using pip:

pip install var_dump

Usage example:

from var_dump import var_dump var_dump(1, {"testkey1": "testval1", "testkey2": "testval2".encode("ascii")}, ["testval"], "test", "test".encode("ascii"), set([1,2,3]))

prints

#0 int(1) #1 dict(2) ['testkey1'] => str(8) "testval1" ['testkey2'] => object(bytes) (b'testval2') #2 list(1) [0] => str(7) "testval" #3 str(4) "test" #4 object(bytes) (b'test') #5 object(set) ({1, 2, 3})

BEST of the best solution, EVER, this utility works so well and does unbelievable formatting of the output. I really strong recommend it!
The library is unmaintained and have unresolved problems and don't accept pull requests (I have 4 pull requests ignored for 2 years-and-counting..)

Cody Casterline · Accepted Answer · 2010-10-26 09:32:17Z

30

PHP's var_export() usually shows a serialized version of the object that can be exec()'d to re-create the object. The closest thing to that in Python is repr()

"For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to eval() [...]"

edited Oct 26, 2010 at 9:32

answered Dec 21, 2008 at 3:02

Cody Casterline

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3 Comments

Paul Biggar Over a year ago

I think you're thinking of var_export.

Victor Farazdagi Over a year ago

yep, var_export in php and repr in python are somewhat related - that's if you want an official string representation of some object - you use repr(). In order to have non-official (read human-readable) you can always force conversion to string: str(object), which produces info similar to php's print_r() (used much more ofter for debugging than var_dump).

mark Over a year ago

Please fix the answer, it's incorrect. As mentioned, either you're talking about var_export or describe var_dump() differently.

Community · Accepted Answer · 2017-05-23 12:02:59Z

So I have taken the answers from this question and another question and came up below. I suspect this is not pythonic enough for most people, but I really wanted something that let me get a deep representation of the values some unknown variable has. I would appreciate any suggestions about how I can improve this or achieve the same behavior easier.

def dump(obj): '''return a printable representation of an object for debugging''' newobj=obj if '__dict__' in dir(obj): newobj=obj.__dict__ if ' object at ' in str(obj) and not newobj.has_key('__type__'): newobj['__type__']=str(obj) for attr in newobj: newobj[attr]=dump(newobj[attr]) return newobj

Here is the usage

class stdClass(object): pass obj=stdClass() obj.int=1 obj.tup=(1,2,3,4) obj.dict={'a':1,'b':2, 'c':3, 'more':{'z':26,'y':25}} obj.list=[1,2,3,'a','b','c',[1,2,3,4]] obj.subObj=stdClass() obj.subObj.value='foobar' from pprint import pprint pprint(dump(obj))

and the results.

{'__type__': '<__main__.stdClass object at 0x2b126000b890>', 'dict': {'a': 1, 'c': 3, 'b': 2, 'more': {'y': 25, 'z': 26}}, 'int': 1, 'list': [1, 2, 3, 'a', 'b', 'c', [1, 2, 3, 4]], 'subObj': {'__type__': '<__main__.stdClass object at 0x2b126000b8d0>', 'value': 'foobar'}, 'tup': (1, 2, 3, 4)}

+1, This is the only answer that actually has var_dump's functionality when it encounters objects
+1 very useful, but it shows an error with "if 'dict' in dir(obj):", I could correct using "if ' instance at ' in str(obj) and obj.__dict__:"
this function only take 1 argument, php's var_dump() take *args

Hassaan · Accepted Answer · 2018-04-12 14:22:49Z

Old topic, but worth a try.

Here is a simple and efficient var_dump function:

def var_dump(var, prefix=''): """ You know you're a php developer when the first thing you ask for when learning a new language is 'Where's var_dump?????' """ my_type = '[' + var.__class__.__name__ + '(' + str(len(var)) + ')]:' print(prefix, my_type, sep='') prefix += ' ' for i in var: if type(i) in (list, tuple, dict, set): var_dump(i, prefix) else: if isinstance(var, dict): print(prefix, i, ': (', var[i].__class__.__name__, ') ', var[i], sep='') else: print(prefix, '(', i.__class__.__name__, ') ', i, sep='')

Sample output:

>>> var_dump(zen) [list(9)]: (str) hello (int) 3 (int) 43 (int) 2 (str) goodbye [list(3)]: (str) hey (str) oh [tuple(3)]: (str) jij (str) llll (str) iojfi (str) call (str) me [list(7)]: (str) coucou [dict(2)]: oKey: (str) oValue key: (str) value (str) this [list(4)]: (str) a (str) new (str) nested (str) list

if type(i) in (list, tuple, dict, set): does not seem to work. When passing an object: TypeError: object of type 'TestPacketDecode' has no len()

Oli · Accepted Answer · 2008-12-21 00:58:36Z

2

print

For your own classes, just def a __str__ method

answered Dec 21, 2008 at 0:58

Oli

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Comments

Peter Mortensen · Accepted Answer · 2014-05-09 05:12:04Z

I don't have PHP experience, but I have an understanding of the Python standard library.

For your purposes, Python has several methods:

logging module;

Object serialization module which is called pickle. You may write your own wrapper of the pickle module.

If your using var_dump for testing, Python has its own doctest and unittest modules. It's very simple and fast for design.

Dmitry Nosov · Accepted Answer · 2009-09-18 09:08:37Z

I use self-written Printer class, but dir() is also good for outputting the instance fields/values.

class Printer: def __init__ (self, PrintableClass): for name in dir(PrintableClass): value = getattr(PrintableClass,name) if '_' not in str(name).join(str(value)): print ' .%s: %r' % (name, value)

The sample of usage:

Printer(MyClass)

if '_' not in str(name).join(str(value)): ^ SyntaxError: invalid syntax

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