How to print a dictionary line by line in Python?

Question

for x in cars:
    print (x)
    for y in cars[x]:
        print (y,':',cars[x][y])

output:

A
color : 2
speed : 70
B
color : 3
speed : 60

You could use the json module for this. The dumps function in this module converts a JSON object into a properly formatted string which you can then print.

import json

cars = {'A':{'speed':70, 'color':2},
        'B':{'speed':60, 'color':3}}

print(json.dumps(cars, indent = 4))

The output looks like

{
    "A": {
        "color": 2,
        "speed": 70
    },
    "B": {
        "color": 3,
        "speed": 60
    }
}

The documentation also specifies a bunch of useful options for this method.

A more generalized solution that handles arbitrarily-deeply nested dicts and lists would be:

def dumpclean(obj):
    if isinstance(obj, dict):
        for k, v in obj.items():
            if hasattr(v, '__iter__'):
                print k
                dumpclean(v)
            else:
                print '%s : %s' % (k, v)
    elif isinstance(obj, list):
        for v in obj:
            if hasattr(v, '__iter__'):
                dumpclean(v)
            else:
                print v
    else:
        print obj

This produces the output:

A
color : 2
speed : 70
B
color : 3
speed : 60

I ran into a similar need and developed a more robust function as an exercise for myself. I'm including it here in case it can be of value to another. In running nosetest, I also found it helpful to be able to specify the output stream in the call so that sys.stderr could be used instead.

import sys

def dump(obj, nested_level=0, output=sys.stdout):
    spacing = '   '
    if isinstance(obj, dict):
        print >> output, '%s{' % ((nested_level) * spacing)
        for k, v in obj.items():
            if hasattr(v, '__iter__'):
                print >> output, '%s%s:' % ((nested_level + 1) * spacing, k)
                dump(v, nested_level + 1, output)
            else:
                print >> output, '%s%s: %s' % ((nested_level + 1) * spacing, k, v)
        print >> output, '%s}' % (nested_level * spacing)
    elif isinstance(obj, list):
        print >> output, '%s[' % ((nested_level) * spacing)
        for v in obj:
            if hasattr(v, '__iter__'):
                dump(v, nested_level + 1, output)
            else:
                print >> output, '%s%s' % ((nested_level + 1) * spacing, v)
        print >> output, '%s]' % ((nested_level) * spacing)
    else:
        print >> output, '%s%s' % (nested_level * spacing, obj)

Using this function, the OP's output looks like this:

{
   A:
   {
      color: 2
      speed: 70
   }
   B:
   {
      color: 3
      speed: 60
   }
}

which I personally found to be more useful and descriptive.

Given the slightly less-trivial example of:

{"test": [{1:3}], "test2":[(1,2),(3,4)],"test3": {(1,2):['abc', 'def', 'ghi'],(4,5):'def'}}

The OP's requested solution yields this:

test
1 : 3
test3
(1, 2)
abc
def
ghi
(4, 5) : def
test2
(1, 2)
(3, 4)

whereas the 'enhanced' version yields this:

{
   test:
   [
      {
         1: 3
      }
   ]
   test3:
   {
      (1, 2):
      [
         abc
         def
         ghi
      ]
      (4, 5): def
   }
   test2:
   [
      (1, 2)
      (3, 4)
   ]
}

I hope this provides some value to the next person looking for this type of functionality.

pprint.pprint() is a good tool for this job:

>>> import pprint
>>> cars = {'A':{'speed':70,
...         'color':2},
...         'B':{'speed':60,
...         'color':3}}
>>> pprint.pprint(cars, width=1)
{'A': {'color': 2,
       'speed': 70},
 'B': {'color': 3,
       'speed': 60}}

You have a nested structure, so you need to format the nested dictionary too:

for key, car in cars.items():
    print(key)
    for attribute, value in car.items():
        print('{} : {}'.format(attribute, value))

This prints:

A
color : 2
speed : 70
B
color : 3
speed : 60

I prefer the clean formatting of yaml:

import yaml
print(yaml.dump(cars))

output:

A:
  color: 2
  speed: 70
B:
  color: 3
  speed: 60