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?

Preserve

I found this looking for the PHP equivalent for pythons repr. Thanks. – Recapitulation

the duplicate question @hop mentions (and the highest voted answer) was much more useful for me – Desdemona

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/… – Gahl

since this thread is closed, see this answer that uses jsonpickle serialization: https://mcmap.net/q/41373/-is-there-a-built-in-function-to-print-all-the-current-properties-and-values-of-an-object – Adham

Answer 1

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.

Kermie

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

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

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

object.__dict__ outputs all the properties of the object – Bartonbartosch

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

Answer 2

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

print vars(foo),vars(bar)

Tajuanatak

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

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

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

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

This answer also works for python pdb debugging with the pp command. e.g. pp vars(my_dict). It should be marked as correct as php var_dump() outputs all the values in the data structure the same as py vars() does. – Milissa

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

Answer 3

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))

Potman

This way is much more better of good. – Delenadeleon

Answer 4

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})

Rigi

Fails on sets - github.com/sha256/python-var-dump/issues/8 – Contortion

BEST of the best solution, EVER, this utility works so well and does unbelievable formatting of the output. I really strong recommend it! – Lithea

@anatolytechtonik that was fixed at 2016-08 ^^ – Samite

Answer 5

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() [...]"

Restoration

I think you're thinking of var_export. – Grimsby

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). – Egression

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

Answer 6

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)}

Preserve

+1, This is the only answer that actually has var_dump's functionality when it encounters objects – Bertold

+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__:" – Pustulant

this function only take 1 argument, php's var_dump() take *args – Samite

Answer 7

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

Guillema

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() – Aspen

Answer 8

print

For your own classes, just def a __str__ method

Lupien

Answer 9

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.

Bloodhound

Answer 10

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)

Crutcher

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