How do I print the variable arguments with names from previous stack?

Question

I would like to define a log function that is called with a message followed by one or more variables to be printed out. So, something like the following:

log( "Oh no, error.", x, d)

log would be defined sorta like:

def log( msg, *arg):
    # Loop through arg, printing caller's variable's name and value.

This would log to a file the following:

Oh no, error.
    x = 5
    d = { foo: "Foo", goo: "Goo" }

Can this be done at all? I can print locals and arguments using inspect, but I don't know if I can iterate through values in the current frame, using the variable names of a previous frame. (locals in inspect.getargvalues(previousFrame) has the names, but lots of other names too.)

Answer 1

I think you can use something like this:

definition

def log(msg, **kwargs):
    print(msg)
    for key, value in kwargs.items():
        print('{0} = {1}'.format(key,value))

definition (if order is a must)

def log(msg, **kwargs):
    print(msg)
    for key, value in sorted(kwargs.items()):
        print('{0} = {1}'.format(key,value))

usage

msg='Oh no, error'
log(msg, x=5, y=6)

output

Oh no, error
y = 6
x = 5

Answer 2

That could be very dirty and may not work from time to time (it does so on my machine), but it seems to do the trick.

Moreover, it doesn't need all these **keargs tricks. You just call log('Message',as,many,args,as,you,want) and that's all.

import inspect, gc

def log(msg,*args):
    #This gets the source code line that has to do with args
    #I mean, that calls log
    code=''.join(inspect.getframeinfo(gc.get_referrers(args)[0].f_back).code_context).strip()
    #get the arguments (except msg)
    c=code.split('log')[1].strip()
    c=c.replace('(','').replace(')','')
    c=c.split(',')[1:]
    if c[-1].endswith(';'):
        c[-1]=c[-1].replace(';','')

    for x in xrange(0,len(c)):
        print c[x],'=',args[x]


a=5; b='hello'

print 'test'

log('hello',a,b);

print 'hello'

Even if log is run from another function, it's OK.