How to print a list in Python "nicely"

Question

In PHP, I can do this:

echo '<pre>'
print_r($array);
echo '</pre>'

In Python, I currently just do this:

print the_list

However, this will cause a big jumbo of data. Is there any way to print it nicely into a readable tree? (with indents)?

Shorten

Answer 1

from pprint import pprint
pprint(the_list)

Hygienic

How ot pretty print to a file? – Durer

Why not just use import pprint? – Longwise

@clankill3r, then you need to use pprint.pprint(the_list) usually it's just a matter of personal preference. I chose to have the extra clutter in the import line in this case. – Hygienic

@Mawg, you can specify an output stream using stream=, the default is stdout. docs.python.org/3/library/pprint.html – Hygienic

It's enabled by default in Ipython REPL – Brunel

@Longwise from pprint import pprint is equivalent to import pprint.pprint as pprint then you use the pprint alias as usual. – Voiture

If your list elements are long enough to wrap, the output may look better using the width option, as in pprint(the_list, width=100). – Buchenwald

Answer 2

Simply by "unpacking" the list in the print function argument and using a newline (\n) as separator.

print(*lst, sep='\n')

lst = ['foo', 'bar', 'spam', 'egg']
print(*lst, sep='\n')

foo
bar
spam
egg

Decay

Nice but unfortunately only available in Python 3. – Capstone

If you really need it in Python 2.7, you could still import the print function from future from __future__ import print_function Thanks for the comment. – Decay

the * is vital, got me for a sec x) – Dragelin

IMO in 2021 where Python 3 is the standard, this should be the accepted answer – Garate

Answer 3

A quick hack while debugging that works without having to import pprint would be to join the list on '\n'.

>>> lst = ['foo', 'bar', 'spam', 'egg']
>>> print '\n'.join(lst)
foo
bar
spam
egg

Exeter

TypeError when the list contains None. – Conversazione

Easy solution and can be formated like `"list: * {}".format('\n * '.join(lst)) – Ridicule

when your list contains something other then strings you should do print '\n'.join(map(str, lst)) – Resplendent

Answer 4

You mean something like...:

>>> print L
['this', 'is', 'a', ['and', 'a', 'sublist', 'too'], 'list', 'including', 'many', 'words', 'in', 'it']
>>> import pprint
>>> pprint.pprint(L)
['this',
 'is',
 'a',
 ['and', 'a', 'sublist', 'too'],
 'list',
 'including',
 'many',
 'words',
 'in',
 'it']
>>> 

...? From your cursory description, standard library module pprint is the first thing that comes to mind; however, if you can describe example inputs and outputs (so that one doesn't have to learn PHP in order to help you;-), it may be possible for us to offer more specific help!

Foresee

Answer 5

import json
some_list = ['one', 'two', 'three', 'four']
print(json.dumps(some_list, indent=4))

Output:

[
    "one",
    "two",
    "three",
    "four"
]

Antoinetteanton

json.dumps adds new line characters in my values for some reason.. – Hope

Answer 6

https://docs.python.org/3/library/pprint.html

If you need the text (for using with curses for example):

import pprint

myObject = []

myText = pprint.pformat(myObject)

Then myText variable will something alike php var_dump or print_r. Check the documentation for more options, arguments.

Heavyladen

Answer 7

For Python 3, I do the same kind of thing as shxfee's answer:

def print_list(my_list):
    print('\n'.join(my_list))

a = ['foo', 'bar', 'baz']
print_list(a)

which outputs

foo
bar
baz

As an aside, I use a similar helper function to quickly see columns in a pandas DataFrame

def print_cols(df):
    print('\n'.join(df.columns))

Pilferage

Answer 8

As the other answers suggest pprint module does the trick.
Nonetheless, in case of debugging where you might need to put the entire list into some log file, one might have to use pformat method along with module logging along with pprint.

import logging
from pprint import pformat

logger = logging.getLogger('newlogger')
handler = logging.FileHandler('newlogger.log')

formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
handler.setFormatter(formatter)

logger.addHandler(handler) 
logger.setLevel(logging.WARNING)

data = [ (i, { '1':'one',
           '2':'two',
           '3':'three',
           '4':'four',
           '5':'five',
           '6':'six',
           '7':'seven',
           '8':'eight',
           })
         for i in xrange(3)
      ]

logger.error(pformat(data))

And if you need to directly log it to a File, one would have to specify an output stream, using the stream keyword. Ref

from pprint import pprint

with open('output.txt', 'wt') as out:
   pprint(myTree, stream=out)

See Stefano Sanfilippo's answer

Panpipe

Answer 9

As other answers have mentioned, pprint is a great module that will do what you want. However if you don't want to import it and just want to print debugging output during development, you can approximate its output.

Some of the other answers work fine for strings, but if you try them with a class object it will give you the error TypeError: sequence item 0: expected string, instance found.

For more complex objects, make sure the class has a __repr__ method that prints the property information you want:

class Foo(object):
    def __init__(self, bar):
        self.bar = bar

    def __repr__(self):
        return "Foo - (%r)" % self.bar

And then when you want to print the output, simply map your list to the str function like this:

l = [Foo(10), Foo(20), Foo("A string"), Foo(2.4)]
print "[%s]" % ",\n ".join(map(str,l))

outputs:

 [Foo - (10),
  Foo - (20),
  Foo - ('A string'),
  Foo - (2.4)]

You can also do things like override the __repr__ method of list to get a form of nested pretty printing:

class my_list(list):
    def __repr__(self):
        return "[%s]" % ",\n ".join(map(str, self))

a = my_list(["first", 2, my_list(["another", "list", "here"]), "last"])
print a

gives

[first,
 2,
 [another,
 list,
 here],
 last]

Unfortunately no second-level indentation but for a quick debug it can be useful.

Dragone

Answer 10

This is a method from raw python that I use very often!

The code looks like this:

list = ["a", "b", "c", "d", "e", "f", "g"]

for i in range(len(list)):
    print(list[i])

output:

a
b
c
d
e
f
g

Jacky

Answer 11

you can also loop trough your list:

def fun():
  for i in x:
    print(i)

x = ["1",1,"a",8]
fun()

Moony

Hello! Please format the code, as it is, it's not easy to follow. Also, global is not meant to be used it that way in python. See #423879 – Jessiajessica