在python中打印变量值。 有什么优雅的格式可以做到吗？

Question

I would like to print variables values in python. eg:

a=3
b=5
print 'blah blah: a = {a}, b = {b}'.format(a=a, b=b)

result is:

blah blah: a = 3, b = 5

My question is how to do it in a short elegant and readable manner.

eg, is there a way to write something like (pseudo code below)

print 'blah blah: {a}, {b}'.format(a,b)

to get the same result?

Thanks! (BTW: i am using python 2.7)

EDIT (clarification): For logging purpose, sometimes i have many variables that i would like to print, so i prefer not doing something like

print 'a={}, b={}, c={},...'.format(a,b,c...) 

because it is a source for bugs (ie I just want to specify the varaible name in the string itself and not care about the order of the variables).

eg, ultimatly, something that looks like

print 'blah blah: {a}, {b}, {c}, {d}, {e}, {f}'.format(c,e,a,f,d,b)

with a result like:

blah blah: a=3, b=5, c=7, d=22, e=2, f=532

Answer 1

You can use your second approach with **locals() instead of a, b . locals() returns a dict containing all local variables. ** unpacks it so you can use it in function calls ( function(**{'a': 3, 'b': 4, 'c': 14}) is the same as function(a=3, b=4, c=14) )

>>> a = 3
>>> b = 4
>>> c = 14
>>> print 'a = {a}, b = {b}'.format(**locals())
a = 3, b = 4

To avoid 'a = {a}' you can do something like

print '{a}, {b}'.format(**{k:'{} = {}'.format(k,v) for (k,v) in locals().iteritems()})

Answer 2

If you know the order that a and b will be in, you don't need to pass them as named arguments in your formatting:

a = 3
b = 5

print('blah blah: a = {}, b = {}'.format(a, b))

Alternatively you could store your variables in a dictionary as below and then use **kwargs unpacking when passing the dict to format.

d = dict(a=3, b=5)

print('blah blah: a = {a}, b = {a}'.format(**d))

Answer 3

import inspect

class fdict(dict):
    def __init__(self, dct):
        for k, v in dct.items():
            self[k] = "{} = {}".format(k, v)

def flocals():
    frame = inspect.currentframe()
    return fdict(frame.f_back.f_locals)

def localformat(string):
    frame = inspect.currentframe()
    dct = fdict(frame.f_back.f_locals)
    return string.format(**dct)

Then import localformat anywhere you want and use this:

>>> a = 5
>>> b = 6
print(localformat('{a}, {b}'))

or call the flocals() to get a string to pass to format.