Develop Reference

Python - 2 arguments instead of one?

Python Code:
class Importer:
from importlib import __import__, reload
from sys import modules
libname = ""
import_count = 0
module = None
def __init__(self, name):
self.libname = name
self.import_count = 0
def importm(self):
if self.libname not in self.modules:
self.module = __import__(self.libname)
else:
print("must reload")
self.module = self.reload(self.module)
self.import_count += 1
# test out Importer
importer = Importer("module")
importer.importm() # prints Hello
importer.importm() # prints Hello
importer.importm() # prints Hello (again)
print(importer.import_count)
The above Python (3.8.1) code is at OnlineGDB, which if you run, will give an error:
TypeError: reload() takes 1 positional argument but 2 were given
When I open up the importlib library in Python, I see this:
# ... (previous code; unnecessary)
_RELOADING = {}
def reload(module): ## this is where reload is defined (one argument)
"""Reload the module and return it.
The module must have been successfully imported before.
"""
if not module or not isinstance(module, types.ModuleType): ## check for type of module
raise TypeError("reload() argument must be a module")
try:
name = module.__spec__.name
except AttributeError:
name = module.__name__
if sys.modules.get(name) is not module: ## other code you (probably) don't have to care about
msg = "module {} not in sys.modules"
raise ImportError(msg.format(name), name=name)
if name in _RELOADING:
return _RELOADING[name]
_RELOADING[name] = module
try:
parent_name = name.rpartition('.')[0]
if parent_name:
try:
parent = sys.modules[parent_name]
except KeyError:
msg = "parent {!r} not in sys.modules"
raise ImportError(msg.format(parent_name),
name=parent_name) from None
else:
pkgpath = parent.__path__
else:
pkgpath = None
target = module
spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
if spec is None:
raise ModuleNotFoundError(f"spec not found for the module {name!r}", name=name)
_bootstrap._exec(spec, module)
# The module may have replaced itself in sys.modules!
return sys.modules[name]
finally:
try:
del _RELOADING[name]
except KeyError:
pass
# ... (After code; unnecessary)
All double hashtag (##) comments are mine
It is clearly visible that reload DOES have 1 argument, and it checks if that argument is a module. In the OGDB (OnineGDB) code, I am only passing one argument (pretty sure) and it is of type module (most likely). If I remove that argument (you can edit the OGDB), it gives:
TypeError: reload() argument must be module
So for some reason, Python keeps thinking I have one more argument than I do actually have. The only way I made it work was editing the importlib file to have reload have two arguments (not a good idea).
I tried running PDB, not helpful.
Can anyone spot anything obviously wrong, like actually having two arguments?

What I needed to do is put the imports outside the class for it to work. Here is the new OGDB. Credits to #L3viathan. Code below:
from importlib import __import__, reload
from sys import modules
class Importer:
libname = ""
import_count = 0
module = None
def __init__(self, name):
self.libname = name
self.import_count = 0
def importm(self):
if self.libname not in modules:
self.module = __import__(self.libname)
else:
print("must reload")
self.module = reload(self.module)
self.import_count += 1
# test out Importer
importer = Importer("module")
importer.importm() # prints Hello
importer.importm() # prints Hello
importer.importm() # prints Hello (again)
print(importer.import_count)

You're having an issue because you're calling self.reload(self.module), which is actually equivalent to calling reload(self, self.module). To see this, try running the following:
class Example:
def some_method(*args):
print(args)
def some_other_method(self):
self.some_method(1)
an_example = Example()
example.some_other_method()
You should see that this prints out 2 arguments, not 1, (the first of which is a reference to self) despite us only passing one argument to some_method, and some_method having no self argument.
It would be better to import the reload method within your importm method (or outside the class altogether!), like so:
def importm(self):
from importlib import __import__, reload
if self.libname not in self.modules:
self.module = __import__(self.libname)
else:
print("must reload")
self.module = reload(self.module)
self.import_count += 1

import mymodule
reload(mymodule)
is how it would work ... Im not sure what your question is from that big wall of text above this is typically used to reset state to its initial state
mymodule.py
x = 5
main.py
from importlib import reload # in py2 you did not need to import it
import mymodule
print(mymodule.x) # 5
mymodule.x = 8
print(mymodule.x) # 8
reload(mymodule)
print(mymodule.x) # 5 again

Python 3 function import error

I am new to python please suggest me the solution
I have two python files first is imtest.py as follows:
d = dict()
if __name__ == '__main__':
def salry(a):
d["f"] = a
print (d)
second is testim.py as follows:
import imtest
a= 90
b = 200
imtest.salry(a)
imtest.salry(b)
When I am trying to run testim.py, it's giving error as :
AttributeError: module 'imtest' has no attribute 'salry'
Then I have modified second file testim.py as follows:
from imtest import salry
a= 90
b = 200
salry(a)
salry(b)
Now I am getting error as
ImportError: cannot import name 'salry'
What could be the error why I am not able to import that function?

The __name__ magic variable has different value depending on whether the module is executed as a script (python imtest.py) or imported from another module. In the first case, __name__ is set to "__main__", in the second case it gets the module's name ("imtest" in your case). The result is that everything in the if __name__ == "__main__": block is only executed when using imtest.py as a script. When you import it from testim.py this part is not executed, so the def salry statement is not executed, so the function is not defined, so you cannot import it.
The solution is quite obvious: put the function definition outside this block:
d = dict()
def salry(a):
d["f"] = a
if __name__ == '__main__':
print (d)

If you want your salary function to be available to other modules, it needs to be in outer scope, so:
d = dict()
def salry(a):
d["f"] = a
print (d)

Instead of this you have to this
d = dict()
def salry(a):
d["f"] = a
print(d)
now you can use it as
from imtest import salry
Now it works fine

Your imtest.py file is imported in your testim.py file, it's not the file that you're running. So it's not your main file, therefore the condition (name == 'main') will be false, and the salry function won't be defined.
You must remove the if statement:
d = dict()
def salry(a):
d["f"] = a
print (d)

How can I access the name a module was imported as?

I want to write a simple tutorial in my Python module foo.
If the module is imported as foo I would like the tutorial to call it foo:
>>> import foo
>>> foo.tutorial()
Please run foo.baz().
However, when the module is imported as bar - I want the tutorial to call it bar:
>>> import foo as bar
>>> bar.tutorial()
Please run bar.baz().
I know that neither __name__ nor __package__ variables would change their value on import ... as ....
To be different from Is it possible to detect way of import of a module in python? - it will be enough for me to know the first alias the module is imported with.

It's not pretty, foolproof, or production worthy, but:
import inspect
import sys
thismod = sys.modules[__name__]
def imported_as():
imported_frame = inspect.currentframe().f_back.f_back
for k, v in imported_frame.f_locals.items():
if v is thismod:
return k
for k, v in imported_frame.f_globals.items():
if v is thismod:
return k
def tutorial():
print('please call {}.baz()'.format(imported_as()))
A tiny explanation:
jump up two stack frames
look at the locals and globals to find the module object that is identical to the module
Why you should really never do this:
it isn't foolproof:
from imports will break this
multiple imports of the same module will nondeterministically give only the first found name
inspect.currentframe is super magical and should generally be avoided in production code

Here is a similar solution to Anthony's. I believe it better handles multiple imports. from imports are still an issue.
import inspect
import re
import readline
def tutorial():
frame = inspect.currentframe().f_back
if "__file__" in frame.f_locals:
f = inspect.getframeinfo(frame)
m = re.search(r"(([^\.]*).*)\.tutorial", f.code_context[0].strip())
if m:
parent,path = m.group(2),m.group(1)
if inspect.ismodule(frame.f_locals[parent]):
print "Please run {}.baz()".format(path)
return
print "Verify import and run foo.baz()"
else:
loc = frame.f_locals
glo = frame.f_globals
local_foo = [(k, v.__name__)for k,v in loc.items() if inspect.ismodule(v) and v.__name__=="foo"]
global_foo = [(k, v.__name__)for k,v in glo.items() if inspect.ismodule(v) and v.__name__=="foo"]
if local_foo and set(local_foo)==set(global_foo):
print "Please run {}.baz()".format(global_foo[-1][0])
elif local_foo and global_foo:
print "Please run {}.baz() in local scope or {}.baz()".format(local_foo[-1][0], global_foo[-1][0])
elif local_foo:
print "Please run {}.baz() in local scope".format(local_foo[-1][0])
elif global_foo:
print "Please run {}.baz()".format(global_foo[-1][0])
else:
n = readline.get_current_history_length()
h = [str(readline.get_history_item(i)) for i in range(n)] + [readline.get_line_buffer()]
h.reverse()
for i in h:
matches = re.findall(r"([A-Za-z0-9_-]*(\.[A-Za-z0-9_-]*)*)\.tutorial", i)
for match in matches:
if _baz_check(glo, match[0]):
print "Please run {}.baz()".format(match[0])
return
print "Verify import and run foo.baz()"
def _baz_check(d, path):
path = path.split(".")
if path[0] not in d:
return False
cur = d[path[0]]
for i in range(1,len(path)):
if not hasattr(cur, path[i]):
return False
cur = getattr(cur, path[i])
return hasattr(cur, "__name__") and cur.__name__ == "foo" and hasattr(cur, "baz")
def baz():
print "Baz"
import foo
foo.tutorial()
import foo as bar
bar.tutorial()
def f():
import foo as local_foo
local_foo.tutorial()
f()
from foo import tutorial
tutorial()
import mod
mod.foo.tutorial()
from mod import foo as dum
dum.tutorial()
Please run foo.baz()
Please run bar.baz()
Please run local_foo.baz()
Verify import and run foo.baz()
Please run mod.foo.baz()
Please run dum.baz()

How can I tell what function called my function? [duplicate]

Python: How to get the caller's method name in the called method?
Assume I have 2 methods:
def method1(self):
...
a = A.method2()
def method2(self):
...
If I don't want to do any change for method1, how to get the name of the caller (in this example, the name is method1) in method2?

inspect.getframeinfo and other related functions in inspect can help:
>>> import inspect
>>> def f1(): f2()
...
>>> def f2():
... curframe = inspect.currentframe()
... calframe = inspect.getouterframes(curframe, 2)
... print('caller name:', calframe[1][3])
...
>>> f1()
caller name: f1
this introspection is intended to help debugging and development; it's not advisable to rely on it for production-functionality purposes.

Shorter version:
import inspect
def f1(): f2()
def f2():
print 'caller name:', inspect.stack()[1][3]
f1()
(with thanks to #Alex, and Stefaan Lippen)

This seems to work just fine:
import sys
print sys._getframe().f_back.f_code.co_name

I would use inspect.currentframe().f_back.f_code.co_name. Its use hasn't been covered in any of the prior answers which are mainly of one of three types:
Some prior answers use inspect.stack but it's known to be too slow.
Some prior answers use sys._getframe which is an internal private function given its leading underscore, and so its use is implicitly discouraged.
One prior answer uses inspect.getouterframes(inspect.currentframe(), 2)[1][3] but it's entirely unclear what [1][3] is accessing.
import inspect
from types import FrameType
from typing import cast
def demo_the_caller_name() -> str:
"""Return the calling function's name."""
# Ref: https://stackoverflow.com/a/57712700/
return cast(FrameType, cast(FrameType, inspect.currentframe()).f_back).f_code.co_name
if __name__ == '__main__':
def _test_caller_name() -> None:
assert demo_the_caller_name() == '_test_caller_name'
_test_caller_name()
Note that cast(FrameType, frame) is used to satisfy mypy.
Acknowlegement: comment by 1313e for an answer.

I've come up with a slightly longer version that tries to build a full method name including module and class.
https://gist.github.com/2151727 (rev 9cccbf)
# Public Domain, i.e. feel free to copy/paste
# Considered a hack in Python 2
import inspect
def caller_name(skip=2):
"""Get a name of a caller in the format module.class.method
`skip` specifies how many levels of stack to skip while getting caller
name. skip=1 means "who calls me", skip=2 "who calls my caller" etc.
An empty string is returned if skipped levels exceed stack height
"""
stack = inspect.stack()
start = 0 + skip
if len(stack) < start + 1:
return ''
parentframe = stack[start][0]
name = []
module = inspect.getmodule(parentframe)
# `modname` can be None when frame is executed directly in console
# TODO(techtonik): consider using __main__
if module:
name.append(module.__name__)
# detect classname
if 'self' in parentframe.f_locals:
# I don't know any way to detect call from the object method
# XXX: there seems to be no way to detect static method call - it will
# be just a function call
name.append(parentframe.f_locals['self'].__class__.__name__)
codename = parentframe.f_code.co_name
if codename != '<module>': # top level usually
name.append( codename ) # function or a method
## Avoid circular refs and frame leaks
# https://docs.python.org/2.7/library/inspect.html#the-interpreter-stack
del parentframe, stack
return ".".join(name)

Bit of an amalgamation of the stuff above. But here's my crack at it.
def print_caller_name(stack_size=3):
def wrapper(fn):
def inner(*args, **kwargs):
import inspect
stack = inspect.stack()
modules = [(index, inspect.getmodule(stack[index][0]))
for index in reversed(range(1, stack_size))]
module_name_lengths = [len(module.__name__)
for _, module in modules]
s = '{index:>5} : {module:^%i} : {name}' % (max(module_name_lengths) + 4)
callers = ['',
s.format(index='level', module='module', name='name'),
'-' * 50]
for index, module in modules:
callers.append(s.format(index=index,
module=module.__name__,
name=stack[index][3]))
callers.append(s.format(index=0,
module=fn.__module__,
name=fn.__name__))
callers.append('')
print('\n'.join(callers))
fn(*args, **kwargs)
return inner
return wrapper
Use:
#print_caller_name(4)
def foo():
return 'foobar'
def bar():
return foo()
def baz():
return bar()
def fizz():
return baz()
fizz()
output is
level : module : name
--------------------------------------------------
3 : None : fizz
2 : None : baz
1 : None : bar
0 : __main__ : foo

You can use decorators, and do not have to use stacktrace
If you want to decorate a method inside a class
import functools
# outside ur class
def printOuterFunctionName(func):
#functools.wraps(func)
def wrapper(self):
print(f'Function Name is: {func.__name__}')
func(self)
return wrapper
class A:
#printOuterFunctionName
def foo():
pass
you may remove functools, self if it is procedural

An alternative to sys._getframe() is used by Python's Logging library to find caller information. Here's the idea:
raise an Exception
immediately catch it in an Except clause
use sys.exc_info to get Traceback frame (tb_frame).
from tb_frame get last caller's frame using f_back.
from last caller's frame get the code object that was being executed in that frame.
In our sample code it would be method1 (not method2) being executed.
From code object obtained, get the object's name -- this is caller method's name in our sample.
Here's the sample code to solve example in the question:
def method1():
method2()
def method2():
try:
raise Exception
except Exception:
frame = sys.exc_info()[2].tb_frame.f_back
print("method2 invoked by: ", frame.f_code.co_name)
# Invoking method1
method1()
Output:
method2 invoked by: method1
Frame has all sorts of details, including line number, file name, argument counts, argument type and so on. The solution works across classes and modules too.

Code:
#!/usr/bin/env python
import inspect
called=lambda: inspect.stack()[1][3]
def caller1():
print "inside: ",called()
def caller2():
print "inside: ",called()
if __name__=='__main__':
caller1()
caller2()
Output:
shahid#shahid-VirtualBox:~/Documents$ python test_func.py
inside: caller1
inside: caller2
shahid#shahid-VirtualBox:~/Documents$

I found a way if you're going across classes and want the class the method belongs to AND the method. It takes a bit of extraction work but it makes its point. This works in Python 2.7.13.
import inspect, os
class ClassOne:
def method1(self):
classtwoObj.method2()
class ClassTwo:
def method2(self):
curframe = inspect.currentframe()
calframe = inspect.getouterframes(curframe, 4)
print '\nI was called from', calframe[1][3], \
'in', calframe[1][4][0][6: -2]
# create objects to access class methods
classoneObj = ClassOne()
classtwoObj = ClassTwo()
# start the program
os.system('cls')
classoneObj.method1()

Hey mate I once made 3 methods without plugins for my app and maybe that can help you, It worked for me so maybe gonna work for you too.
def method_1(a=""):
if a == "method_2":
print("method_2")
if a == "method_3":
print("method_3")
def method_2():
method_1("method_2")
def method_3():
method_1("method_3")
method_2()

How to make global imports from a function?

I fear that this is a messy way to approach the problem but...
let's say that I want to make some imports in Python based on some conditions.
For this reason I want to write a function:
def conditional_import_modules(test):
if test == 'foo':
import onemodule, anothermodule
elif test == 'bar':
import thirdmodule, and_another_module
else:
import all_the_other_modules
Now how can I have the imported modules globally available?
For example:
conditional_import_modules(test='bar')
thirdmodule.myfunction()

Imported modules are just variables - names bound to some values. So all you need is to import them and make them global with global keyword.
Example:
>>> math
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'math' is not defined
>>> def f():
... global math
... import math
...
>>> f()
>>> math
<module 'math' from '/usr/local/lib/python2.6/lib-dynload/math.so'>

You can make the imports global within a function like this:
def my_imports(module_name):
globals()[module_name] = __import__(module_name)

I've just had the similar problem, here is my solution:
class GlobalImport:
def __enter__(self):
return self
def __call__(self):
import inspect
self.collector = inspect.getargvalues(inspect.getouterframes(inspect.currentframe())[1].frame).locals
def __exit__(self, *args):
globals().update(self.collector)
then, anywhere in the code:
with GlobalImport() as gi:
import os, signal, atexit, threading, _thread
# whatever you want it won't remain local
# if only
gi()
# is called before the end of this block
# there you go: use os, signal, ... from whatever place of the module

You can use the built-in function __import__ to conditionally import a module with global scope.
To import a top level module (think: import foo):
def cond_import():
global foo
foo = __import__('foo', globals(), locals())
Import from a hierarchy (think: import foo.bar):
def cond_import():
global foo
foo = __import__('foo.bar', globals(), locals())
Import from a hierarchy and alias (think: import foo.bar as bar):
def cond_import():
global bar
foo = __import__('foo.bar', globals(), locals())
bar = foo.bar

I like #badzil approach.
def global_imports(modulename,shortname = None, asfunction = False):
if shortname is None:
shortname = modulename
if asfunction is False:
globals()[shortname] = __import__(modulename)
else:
globals()[shortname] = eval(modulename + "." + shortname)
So something that is traditionally in a class module:
import numpy as np
import rpy2
import rpy2.robjects as robjects
import rpy2.robjects.packages as rpackages
from rpy2.robjects.packages import importr
Can be transformed into a global scope:
global_imports("numpy","np")
global_imports("rpy2")
global_imports("rpy2.robjects","robjects")
global_imports("rpy2.robjects.packages","rpackages")
global_imports("rpy2.robjects.packages","importr",True)
May have some bugs, which I will verify and update. The last example could also have an alias which would be another "shortname" or a hack like "importr|aliasimportr"

I like #rafał grabie approach. As it even support importing all.
i.e.
from os import *
(Despite it being bad practice XD )
Not allowed to comment, but here is a python 2.7 version.
Also removed the need to call the function at the end.
class GlobalImport:
def __enter__(self):
return self
def __exit__(self, *args):
import inspect
collector = inspect.getargvalues(inspect.getouterframes(inspect.currentframe())[1][0]).locals
globals().update(collector)
def test():
with GlobalImport() as gi:
## will fire a warning as its bad practice for python.
from os import *
test()
print path.exists(__file__)

I like the answer from #maxschlepzig.
There is a bug in the approach that if you directly import a function it will not work.
For example,
global_imports("tqdm", "tqdm, True)
does not work, because the module is not imported. And this
global_imports("tqdm")
global_imports("tqdm", "tqdm, True)
works.
I change #maxschlepzig's answer a bit. Using fromlist so you can load function or module with "From" statement in a uniform way.
def global_imports(object_name: str,
short_name: str = None,
context_module_name: str = None):
"""import from local function as global import
Use this statement to import inside a function,
but effective as import at the top of the module.
Args:
object_name: the object name want to import,
could be module or function
short_name: the short name for the import
context_module_name: the context module name in the import
example usage:
import os -> global_imports("os")
import numpy as np -> global_imports("numpy", "np")
from collections import Counter ->
global_imports("Counter", None, "collections")
from google.cloud import storage ->
global_imports("storage", None, "google.cloud")
"""
if not short_name:
short_name = object_name
if not context_module_name:
globals()[short_name] = __import__(object_name)
else:
context_module = __import__(context_module_name,
fromlist=[object_name])
globals()[short_name] = getattr(context_module, object_name)

You could have this function return the names of the modules you want to import, and then use
mod == __import__(module_name)

Step-1: config.py, config_v2.py, rnd.py in same directory/folder
Step-2: config.py
HIGH_ATTENDANCE_COUNT_MIN = 0
Step-3: config_v2.py
HIGH_ATTENDANCE_COUNT_MIN = 5
Step-4: rnd.py
def versioning_test(v):
global config
if v == 'v1':
config = __import__('config', globals(), locals())
if v == 'v2':
config = __import__('config_v2', globals(), locals())
def version_test_in_another_function():
print('version_test_in_another_function: HIGH_ATTENDANCE_COUNT_MIN: ', config.HIGH_ATTENDANCE_COUNT_MIN)
versioning_test("v2")
version_test_in_another_function()
Step-5: $ python3 rnd.py
<<output>>: version_test_in_another_function: HIGH_ATTENDANCE_COUNT_MIN: 5

It is now recommended (for Python 3), to use the importlib
https://docs.python.org/3/reference/import.html#importlib
eg: globals()["np"] = importlib.import_module("numpy")
and you can now execute "np.array([1,2,3])" afterwards.
There are also other ways of importing that you might prefer. Consider seeing the aforementioned documentation.