Readably print out a python dict() sorted by key

Question

I would like to print a python dictionary to a file using PrettyPrinter (for human readability) but have the dictionary be sorted by key in the output file to further improv

Answer 1

I had the same problem you had. I used a for loop with the sorted function passing in the dictionary like so:

for item in sorted(mydict):
    print(item)

Answer 2

The Python pprint module actually already sorts dictionaries by key. In versions prior to Python 2.5, the sorting was only triggered on dictionaries whose pretty-printed representation spanned multiple lines, but in 2.5.X and 2.6.X, all dictionaries are sorted.

Generally, though, if you're writing data structures to a file and want them human-readable and writable, you might want to consider using an alternate format like YAML or JSON. Unless your users are themselves programmers, having them maintain configuration or application state dumped via pprint and loaded via eval can be a frustrating and error-prone task.

Answer 3

Another short oneliner:

mydict = {'c': 1, 'b': 2, 'a': 3}
print(*sorted(mydict.items()), sep='\n')

Answer 4

Another alternative :

>>> mydict = {'a':1, 'b':2, 'c':3}
>>> import json

Then with python2 :

>>> print json.dumps(mydict, indent=4, sort_keys=True) # python 2
{
    "a": 1, 
    "b": 2, 
    "c": 3
}

or with python 3 :

>>> print(json.dumps(mydict, indent=4, sort_keys=True)) # python 3
{
    "a": 1, 
    "b": 2, 
    "c": 3
}

Answer 5

An easy way to print the sorted contents of the dictionary, in Python 3:

>>> dict_example = {'c': 1, 'b': 2, 'a': 3}
>>> for key, value in sorted(dict_example.items()):
...   print("{} : {}".format(key, value))
... 
a : 3
b : 2
c : 1

The expression dict_example.items() returns tuples, which can then be sorted by sorted():

>>> dict_example.items()
dict_items([('c', 1), ('b', 2), ('a', 3)])
>>> sorted(dict_example.items())
[('a', 3), ('b', 2), ('c', 1)]

Below is an example to pretty print the sorted contents of a Python dictionary's values.

for key, value in sorted(dict_example.items(), key=lambda d_values: d_values[1]): 
    print("{} : {}".format(key, value))

Answer 6

I wrote the following function to print dicts, lists, and tuples in a more readable format:

def printplus(obj):
    """
    Pretty-prints the object passed in.

    """
    # Dict
    if isinstance(obj, dict):
        for k, v in sorted(obj.items()):
            print u'{0}: {1}'.format(k, v)

    # List or tuple            
    elif isinstance(obj, list) or isinstance(obj, tuple):
        for x in obj:
            print x

    # Other
    else:
        print obj

Example usage in iPython:

>>> dict_example = {'c': 1, 'b': 2, 'a': 3}
>>> printplus(dict_example)
a: 3
b: 2
c: 1

>>> tuple_example = ((1, 2), (3, 4), (5, 6), (7, 8))
>>> printplus(tuple_example)
(1, 2)
(3, 4)
(5, 6)
(7, 8)