How do I say "Is this a function"?

[John Henry]

How do I determine is something a function?

For instance, I don't want to relying on exceptions below:

def f1():
print "In f1"

def f3():
print "In f3"

def others():
print "In others"

for i in xrange(1,3):
fct = "f%d()"%(i+1)
try:
exec fct
except:
others()

I wish to say:

if value of fct is a funtion, invoke it, otherwise invoke others().

Thanks,

[Dan Bishop]

On Apr 26, 6:17 pm, John Henry <[e-mail]:

How do I determine is something a function?

For instance, I don't want to relying on exceptions below:

def f1():
print "In f1"

def f3():
print "In f3"

def others():
print "In others"

for i in xrange(1,3):
fct = "f%d()"%(i+1)
try:
exec fct
except:
others()

I wish to say:

if value of fct is a funtion, invoke it, otherwise invoke others().

Thanks,

hasattr(fct, '__call__')

And be careful about using the exec statement.

[alex.gaynor]

callable(func) returns whether something is callable(will return true
for classes, functions, and objects with __call__ methods).

On Apr 26, 6:25*pm, Dan Bishop <[e-mail]:

On Apr 26, 6:17 pm, John Henry <[e-mail]:

How do I determine is something a function?

For instance, I don't want to relying on exceptions below:

def f1():
* *print "In f1"

def f3():
* *print "In f3"

def others():
* *print "In others"

for i in xrange(1,3):
* *fct = "f%d()"%(i+1)
* *try:
* * * exec fct
* *except:
* * * others()

I wish to say:

* *if value of fct is a funtion, invoke it, otherwise invoke others().

Thanks,

hasattr(fct, '__call__')

And be careful about using the exec statement.

[Martin P. Hellwig]

John Henry wrote:

How do I determine is something a function?

For instance, I don't want to relying on exceptions below:

def f1():
print "In f1"

def f3():
print "In f3"

def others():
print "In others"

for i in xrange(1,3):
fct = "f%d()"%(i+1)
try:
exec fct
except:
others()

I wish to say:

if value of fct is a funtion, invoke it, otherwise invoke others().

Thanks,

One way I would think of is:
str(type(fct)) == "<type 'function'>"

--
mph

[John Machin]

Dan Bishop wrote:

On Apr 26, 6:17 pm, John Henry <[e-mail]:

>How do I determine is something a function?

For instance, I don't want to relying on exceptions below:

And why not?

>>
def f1():
print "In f1"

def f3():
print "In f3"

def others():
print "In others"

for i in xrange(1,3):
fct = "f%d()"%(i+1)
try:
exec fct
except:
others()

I wish to say:

if value of fct is a funtion, invoke it, otherwise invoke others().

Thanks,

hasattr(fct, '__call__')

And be careful about using the exec statement.

1. In the OP's code, fct is a string, e.g. "f2()", so hasattr(fct,
'__call__') will never return True.

2. Objects other than functions have a __call__ attribute. Some callable
objects don't have a __call__ attribute.

3. Use __doubleunderscore__ things only when you need them and only when
you know what you are doing. There are high-level built-in functions
such as callable and isinstance that can be used for such tests. The
literal answer to the OP's question is:

from types import FunctionType
if isinstance(fct, FunctionType):
do_something()

Something like the following will do the required trick (find callables
in the global namespace whose name matches a pattern) without using the
dreaded exec. Note I've left out the logic to call others; the OP's code
will call others once for each missing function ... let's leave him to
sort out whether that's a good idea or that should be changed to calling
it only once if all functions are missing.

>>def f1():

.... print "in f1"
....

>>def f3():

.... print "in f3"
....

>>globdict = globals()
globdict # output prettied manually

{'f1': <function f1 at 0x00BA0470>,
'f3': <function f3 at 0x00BA04F0>,
'__builtins__': <module '__builtin__' (built-in)>,
'__name__': '__main__',
'__doc__': None}

>>for i in xrange(1, 4): ### upper bound 3 probably a bug

.... fname = "f%d" % i
.... if fname in globdict:
.... func = globdict[fname]
.... if callable(func):
.... func()
....
in f1
in f3

>>>

Cheers,
John

[=?ISO-8859-1?Q?=22Martin_v=2E_L=F6wis=22?=]

def f1():

print "In f1"

def f3():
print "In f3"

def others():
print "In others"

for i in xrange(1,3):
fct = "f%d()"%(i+1)
try:
exec fct
except:
others()

I'd write that as

for i in xrange(1,3):
globals().get("f%d" % (i+1), others)()

Regards,
Martin

[John Henry]

On Apr 26, 6:08*pm, "Martin v. Löwis" <[e-mail]:

def f1():
* *print "In f1"

def f3():
* *print "In f3"

def others():
* *print "In others"

for i in xrange(1,3):
* *fct = "f%d()"%(i+1)
* *try:
* * * exec fct
* *except:
* * * others()

I'd write that as

for i in xrange(1,3):
* * globals().get("f%d" % (i+1), others)()

Regards,
Martin

Perfect. Works great. No EXEC.

You guys are great.

[Lie]

On Apr 27, 11:01*am, John Henry <[e-mail]:

On Apr 26, 6:08*pm, "Martin v. Löwis" <[e-mail]:

def f1():
* *print "In f1"

def f3():
* *print "In f3"

def others():
* *print "In others"

for i in xrange(1,3):
* *fct = "f%d()"%(i+1)
* *try:
* * * exec fct
* *except:
* * * others()

I'd write that as

for i in xrange(1,3):
* * globals().get("f%d" % (i+1), others)()

Regards,
Martin

Perfect. *Works great. *No EXEC.

You guys are great.

If you just want to avoid exec, why not:

def f1:
print "In f1"
def f3:
print "In f3"

class f4(object):
def __init__(self):
print "In f4"

def others:
print "Since all else failed, I'm in others."

f2 = "NAF -Not a Function"

flist = [f1, f2, f3, f4]
for fct in flist:
try:
fct()
except TypeError:
others()

It's readable, and it's fast if there's just a few "hard fault" (try-
except works best when it usually succeed and just fails once or
twice), and it's Pythonic too (Easier to ask forgiveness than to ask
permission). The difference between this and the explicit type
checking is that this allows a class (like f4) to pass since a Class
Constructor & Initiator is a callable function too, depending on your
need, you might want to consider class constructor as a function too.

[John Henry]

On Apr 27, 10:49 am, Lie <[e-mail]:

On Apr 27, 11:01 am, John Henry <[e-mail]:

On Apr 26, 6:08 pm, "Martin v. Löwis" <[e-mail]:

def f1():
print "In f1"

def f3():
print "In f3"

def others():
print "In others"

for i in xrange(1,3):
fct = "f%d()"%(i+1)
try:
exec fct
except:
others()

I'd write that as

for i in xrange(1,3):
globals().get("f%d" % (i+1), others)()

Regards,
Martin

Perfect. Works great. No EXEC.

You guys are great.

If you just want to avoid exec, why not:

def f1:
print "In f1"
def f3:
print "In f3"

class f4(object):
def __init__(self):
print "In f4"

def others:
print "Since all else failed, I'm in others."

f2 = "NAF -Not a Function"

flist = [f1, f2, f3, f4]
for fct in flist:
try:
fct()
except TypeError:
others()

It's readable, and it's fast if there's just a few "hard fault" (try-
except works best when it usually succeed and just fails once or
twice), and it's Pythonic too (Easier to ask forgiveness than to ask
permission). The difference between this and the explicit type
checking is that this allows a class (like f4) to pass since a Class
Constructor & Initiator is a callable function too, depending on your
need, you might want to consider class constructor as a function too.

The reason I didn't want to do that is because when something goes
wrong inside the fcts, others gets executed. I wanted the program to
crash and burn rather than running others.