Run function from the command line

Question

I have this code:

def hello():
    return 'Hi :)'

How would I run this directly from the command line?

---

_{See also: What does if __name__ == "__main__": do? to explain the standard idiom for getting the code started;
Why doesn't the main() function run when I start a Python script? Where does the script start running (what is its entry point)? for why things like this are necessary}

Answer 1

With the -c (command) argument (assuming your file is named foo.py):

$ python -c 'import foo; print foo.hello()'

Alternatively, if you don't care about namespace pollution:

$ python -c 'from foo import *; print hello()'

And the middle ground:

$ python -c 'from foo import hello; print hello()'

Answer 2

Just put hello() somewhere below the function and it will execute when you do python your_file.py

For a neater solution you can use this:

if __name__ == '__main__':
    hello()

That way the function will only be executed if you run the file, not when you import the file.

Answer 3

add this snippet to the bottom of your script

def myfunction():
    ...


if __name__ == '__main__':
    globals()[sys.argv[1]]()

You can now call your function by running

python myscript.py myfunction

This works because you are passing the command line argument (a string of the function's name) into locals, a dictionary with a current local symbol table. The parantheses at the end will make the function be called.

update: if you would like the function to accept a parameter from the command line, you can pass in sys.argv[2] like this:

def myfunction(mystring):
    print(mystring)


if __name__ == '__main__':
    globals()[sys.argv[1]](sys.argv[2])

This way, running python myscript.py myfunction "hello" will output hello.

Answer 4

python -c 'from myfile import hello; hello()' where myfile must be replaced with the basename of your Python script. (E.g., myfile.py becomes myfile).

However, if hello() is your "permanent" main entry point in your Python script, then the usual way to do this is as follows:

def hello():
    print "Hi :)"

if __name__ == "__main__":
    hello()

This allows you to execute the script simply by running python myfile.py or python -m myfile.

Some explanation here: __name__ is a special Python variable that holds the name of the module currently being executed, except when the module is started from the command line, in which case it becomes "__main__".

Answer 5

We can write something like this. I have used with python-3.7.x

import sys

def print_fn():
    print("Hi")

def sum_fn(a, b):
    print(a + b)

if __name__ == "__main__":
    args = sys.argv
    # args[0] = current file
    # args[1] = function name
    # args[2:] = function args : (*unpacked)
    globals()[args[1]](*args[2:])

python demo.py print_fn
python demo.py sum_fn 5 8

Answer 6

I wrote a quick little Python script that is callable from a bash command line. It takes the name of the module, class and method you want to call and the parameters you want to pass. I call it PyRun and left off the .py extension and made it executable with chmod +x PyRun so that I can just call it quickly as follow:

./PyRun PyTest.ClassName.Method1 Param1

Save this in a file called PyRun

#!/usr/bin/env python
#make executable in bash chmod +x PyRun

import sys
import inspect
import importlib
import os

if __name__ == "__main__":
    cmd_folder = os.path.realpath(os.path.abspath(os.path.split(inspect.getfile( inspect.currentframe() ))[0]))
    if cmd_folder not in sys.path:
        sys.path.insert(0, cmd_folder)

    # get the second argument from the command line      
    methodname = sys.argv[1]

    # split this into module, class and function name
    modulename, classname, funcname = methodname.split(".")

    # get pointers to the objects based on the string names
    themodule = importlib.import_module(modulename)
    theclass = getattr(themodule, classname)
    thefunc = getattr(theclass, funcname)

    # pass all the parameters from the third until the end of 
    # what the function needs & ignore the rest
    args = inspect.getargspec(thefunc)
    z = len(args[0]) + 2
    params=sys.argv[2:z]
    thefunc(*params)

Here is a sample module to show how it works. This is saved in a file called PyTest.py:

class SomeClass:
 @staticmethod
 def First():
     print "First"

 @staticmethod
 def Second(x):
    print(x)
    # for x1 in x:
    #     print x1

 @staticmethod
 def Third(x, y):
     print x
     print y

class OtherClass:
    @staticmethod
    def Uno():
        print("Uno")

Try running these examples:

./PyRun PyTest.SomeClass.First
./PyRun PyTest.SomeClass.Second Hello
./PyRun PyTest.SomeClass.Third Hello World
./PyRun PyTest.OtherClass.Uno
./PyRun PyTest.SomeClass.Second "Hello"
./PyRun PyTest.SomeClass.Second \(Hello, World\)

Note the last example of escaping the parentheses to pass in a tuple as the only parameter to the Second method.

If you pass too few parameters for what the method needs you get an error. If you pass too many, it ignores the extras. The module must be in the current working folder, put PyRun can be anywhere in your path.

Answer 7

Let's make this a little easier on ourselves and just use a module...

Try: pip install compago

Then write:

import compago
app = compago.Application()

@app.command
def hello():
    print "hi there!"

@app.command
def goodbye():
    print "see ya later."

if __name__ == "__main__":
    app.run()

Then use like so:

$ python test.py hello
hi there!

$ python test.py goodbye
see ya later.

Note: There's a bug in Python 3 at the moment, but works great with Python 2.

Edit: An even better option, in my opinion is the module fire by Google which makes it easy to also pass function arguments. It is installed with pip install fire. From their GitHub:

Here's a simple example.

import fire

class Calculator(object):
  """A simple calculator class."""

  def double(self, number):
    return 2 * number

if __name__ == '__main__':
  fire.Fire(Calculator)

Then, from the command line, you can run:

python calculator.py double 10  # 20
python calculator.py double --number=15  # 30

Answer 8

Interestingly enough, if the goal was to print to the command line console or perform some other minute python operation, you can pipe input into the python interpreter like so:

echo print("hi:)") | python

as well as pipe files..

python < foo.py

*Note that the extension does not have to be .py for the second to work. **Also note that for bash you may need to escape the characters

echo print\(\"hi:\)\"\) | python

Answer 9

I had a requirement of using various python utilities (range, string, etc.) on the command line and had written the tool pyfunc specifically for that. You can use it to enrich you command line usage experience:

 $ pyfunc -m range -a 1 7 2
 1
 3
 5

 $ pyfunc -m string.upper -a test
 TEST

 $ pyfunc -m string.replace -a 'analyze what' 'what' 'this'
 analyze this

Answer 10

If you install the runp package with pip install runp its a matter of running:

runp myfile.py hello

You can find the repository at: https://github.com/vascop/runp

Answer 11

This script is similar to other answers here, but it also lists the available functions, with arguments and docstrings:

"""Small script to allow functions to be called from the command line.
Run this script without argument to list the available functions:

    $ python many_functions.py
    Available functions in many_functions.py:

    python many_functions.py a  : Do some stuff

    python many_functions.py b  : Do another stuff

    python many_functions.py c x y : Calculate x + y

    python many_functions.py d  : ?

Run this script with arguments to try to call the corresponding function:

    $ python many_functions.py a
    Function a

    $ python many_functions.py c 3 5
    3 + 5 = 8

    $ python many_functions.py z
    Function z not found
"""

import sys
import inspect

#######################################################################
#                         Your functions here                         #
#######################################################################

def a():
    """Do some stuff"""
    print("Function a")

def b():
    """Do another stuff"""
    a()
    print("Function b")

def c(x, y):
    """Calculate x + y"""
    print(f"{x} + {y} = {int(x) + int(y)}")

def d():
    # No doc
    print("Function d")

#######################################################################
#         Some logic to find and display available functions          #
#######################################################################

def _get_local_functions():
    local_functions = {}
    for name, obj in inspect.getmembers(sys.modules[__name__]):
        if inspect.isfunction(obj) and not name.startswith('_') and obj.__module__ == __name__:
            local_functions[name] = obj
    return local_functions

def _list_functions(script_name):
    print(f"Available functions in {script_name}:")
    for name, f in _get_local_functions().items():
        print()
        arguments = inspect.signature(f).parameters
        print(f"python {script_name} {name} {' '.join(arguments)} : {f.__doc__ or '?'}")


if __name__ == '__main__':
    script_name, *args = sys.argv
    if args:
        functions = _get_local_functions()
        function_name = args.pop(0)
        if function_name in functions:
            function = functions[function_name]
            function(*args)
        else:
            print(f"Function {function_name} not found")
            _list_functions(script_name)
    else:
        _list_functions(script_name)

Run this script without argument to list the available functions:

$ python many_functions.py
Available functions in many_functions.py:

python many_functions.py a  : Do some stuff

python many_functions.py b  : Do another stuff

python many_functions.py c x y : Calculate x + y

python many_functions.py d  : ?

Run this script with arguments to try to call the corresponding function:

$ python many_functions.py a
Function a

$ python many_functions.py c 3 5
3 + 5 = 8

$ python many_functions.py z
Function z not found

Answer 12

Something like this: call_from_terminal.py

# call_from_terminal.py
# Ex to run from terminal
# ip='"hi"'
# python -c "import call_from_terminal as cft; cft.test_term_fun(${ip})"
# or
# fun_name='call_from_terminal'
# python -c "import ${fun_name} as cft; cft.test_term_fun(${ip})"
def test_term_fun(ip):
    print ip

This works in bash.

$ ip='"hi"' ; fun_name='call_from_terminal' 
$ python -c "import ${fun_name} as cft; cft.test_term_fun(${ip})"
hi

Answer 13

Below is the Odd_Even_function.py file that has the definition of the function.

def OE(n):
    for a in range(n):
        if a % 2 == 0:
            print(a)
        else:
            print(a, "ODD")

Now to call the same from Command prompt below are the options worked for me.

Options 1 Full path of the exe\python.exe -c "import Odd_Even_function; Odd_Even_function.OE(100)"

Option 2 Full path of the exe\python.exe -c "from Odd_Even_function import OE; OE(100)"

Thanks.

Answer 14

It is always an option to enter python on the command line with the command python

then import your file so import example_file

then run the command with example_file.hello()

This avoids the weird .pyc copy function that crops up every time you run python -c etc.

Maybe not as convenient as a single-command, but a good quick fix to text a file from the command line, and allows you to use python to call and execute your file.

Answer 15

python3 inspect.signature retrieves the details of a python function. Then build a list of args and a dictionary of kwargs using sys.argv that is then bound to the function signature.

This enables you to call functions of a file in a "more" pythonic way.

$ python3 myscript.py foo baz
"foo(bar=baz)"

$ python3 myscript.py foo bar=baz
"foo(bar=baz)"

# file: myscript.py

import inspect
import sys

def foo(bar: str):
    print(f"foo(bar={bar}")

if __name__ == "__main__":
    # args[0]  = current file
    # args[1]  = function name
    # args[2:] = function args : (*unpacked)
    func = globals()[sys.argv[1]]
    args = list(arg for arg in sys.argv[2:] if not "=" in arg)
    kwargs = dict(arg.split("=") for arg in sys.argv[2:] if "=" in arg)
    try:
        # Binds / maps the command-line arguments to the function
        bound_arguments = inspect.signature(func).bind(*args, **kwargs)
        func(*bound_arguments.args, **bound_arguments.kwargs)
    except TypeError as e:
        raise e

Answer 16

This function cannot be run from the command line as it returns a value which will go unhanded. You can remove the return and use print instead

Answer 17

Use the python-c tool (pip install python-c) and then simply write:

$ python-c foo 'hello()'

or in case you have no function name clashes in your python files:

$ python-c 'hello()'

Answer 18

First you have to call the function as they told you or the founction will display nothing in the output, after that save the file and copy the path of the file by right click to the folder of the file and click on"copy file" then go to terminal and write: - cd "the path of the file" - python "name of the file for example (main.py)" after that it will display the output of your code.

Answer 19

Make your life easier, install Spyder. Open your file then run it (click the green arrow). Afterwards your hello() method is defined and known to the IPython Console, so you can call it from the console.