使用python中的格式打印混合类型字典

Question

I have

d = {'a':'Ali', 'b':2341, 'c':0.2424242421, 'p':3.141592}

I want to print it out to std but I want format the numbers, like remove the excessive decimal places, something like

{'a':'Ali', 'b':2341, 'c':0.24, 'p':3.14}

obviously I can go through all the items and see if they are a 'type' I want to format and format them and print the results,

But is there a better way to format all the numbers in a dictionary when __str__() ing or in someway getting a string out to print?

EDIT:
I am looking for some magic like:

'{format only floats and ignore the rest}'.format(d)

or something from the yaml world or similar.

Answer 1

You can use round for rounding the floats to a given precision. To identify floats use isinstance :

>>> {k:round(v,2) if isinstance(v,float) else v for k,v in d.iteritems()}
{'a': 'Ali', 'p': 3.14, 'c': 0.24, 'b': 2341}

help on round :

>>> print round.__doc__
round(number[, ndigits]) -> floating point number

Round a number to a given precision in decimal digits (default 0 digits).
This always returns a floating point number.  Precision may be negative.

Update:

You can create a subclass of dict and override the behaviour of __str__ :

class my_dict(dict):                                              
    def __str__(self):
        return str({k:round(v,2) if isinstance(v,float) else v 
                                                    for k,v in self.iteritems()})
...     
>>> d = my_dict({'a':'Ali', 'b':2341, 'c':0.2424242421, 'p':3.141592})
>>> print d
{'a': 'Ali', 'p': 3.14, 'c': 0.24, 'b': 2341}
>>> "{}".format(d)
"{'a': 'Ali', 'p': 3.14, 'c': 0.24, 'b': 2341}"
>>> d
{'a': 'Ali', 'p': 3.141592, 'c': 0.2424242421, 'b': 2341}

Answer 2

To convert float to two decimal places, do this:

a = 3.141592
b = float("%.2f" % a) #b will have 2 decimal places!
you could also do:
b = round(a,2)

So to beautify your dictionary:

newdict = {}
for x in d:
    if isinstance(d[x],float):
        newdict[x] = round(d[x],2)
    else:
        newdict[x] = d[x]

you could also do:

newdict = {}
for x in d:
    if isinstance(d[x],float):
        newdict[x] = float("%.2f" % d[x])
    else:
        newdict[x] = d[x]

though the first one is recommended!