How to run python function from command line

Question

This is my code:

def isPrime(n):
    if n>1:
        for i in range(2, n):
            if (n%i)== 0:
                print(n, "is not a prime number")
                print(i, "*", n//i, "=", n)
                break
        else:
            print(n, "is a prime number")
    else:
        print(n, "is not a prime number")

Earlier I have used idle and Jupyter notebook but now I am trying to run it via command line and I don't know how to enter argument for the function defined. I'm using cmd for the first time for running scripts. This is what it shows:

Does this answer your question? how to run python files in windows command prompt? — Tomerikoo
– Tomerikoo, Commented Jan 31, 2021 at 10:09
You have a few mixed problems here. In the command line, you entered an interactive Python interpreter (by doing python). Inside a Python interpreter, you can import your py file by import prime and then run the function by calling it: prime.isPrime(10). If you want to run the file from the command line, you need to do python prime.py but you have to have some runnable code. Right now you just define a function. You need to also call it inside the file, probably under a main guard/function — Tomerikoo
– Tomerikoo, Commented Jan 31, 2021 at 10:13

YamiAtem · Accepted Answer · 2021-01-31 10:10:13Z

5

You can use the flag -c while doing python like this:

python -c 'isPrime(11)'

you can also import this way as well

python -c 'import foo; foo.isPrime(2)'

or do this

python -c 'from foo import isPrime; foo.isPrime(n)'

answered Jan 31, 2021 at 10:10

YamiAtem

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1 Comment

Edouard Over a year ago

For the last one: python3 -c 'from foo import isPrime; isPrime(...)'

Mirdrop · Accepted Answer · 2022-08-05 16:45:58Z

3

Curiously, using cmd.exe on my computer, the -c function only works if you use double quotes on the outside (ie the example above may not have worked because it used single quotes):

python -c 'print("It worked!")'

shows no output, while

python -c "print('It worked!')"

Prints 'It worked!' as expected. I presume this is particular to windows cmd.exe

answered Aug 5, 2022 at 16:45

Mirdrop

311 bronze badge

1 Comment

jshd Over a year ago

This was very helpful as I couldn't understand what was wrong. Not only did I not get a print() output when using single quotes, but I also got a SyntaxError when I tried to do an import. Using double quotes solved it, so thanks.

Leonardo Scotti · Accepted Answer · 2021-01-31 10:16:31Z

to do this you have to open the cmd

then first start python interpreter:

C:\Users\YourUser> py

or

C:\Users\YourUser> python

(it depends form your python version)

then will appear this:

Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:20:19) [MSC v.1925 32 bit (In
tel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

NOTE:

this message can be different because of your python version or your computer >system

now you only have to import your file as a module and then call your function like this:

>>> import yourfilename
>>> yourfilename.foo(args_to_be_passed_to_your_function)

NOTE:

to fo this your file has to be in your cwd (current work directory) or in >your python path

if instead you want to execute your file you have to do:

>>> path/to/your/filename.py

to quit the python interpreter write:

>>> exit()

user15249015 · Accepted Answer · 2022-04-23 15:07:59Z

0

Actually the -c solutions above (such as python -c 'isPrime(11)') did not work for me, as they leave a blank line. I can call a function from a Python environment itself, so first I locate, then run:

C://Desktop/MyPythonFiles/> python

    >>> import myfunction; myfunction.isPrime(13)

The only difference with Leonardo's answer is that you may write the call on the same line using a semicolon.

edited Apr 23, 2022 at 15:07

answered Apr 23, 2022 at 15:05

user15249015

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1 Comment

Chris Over a year ago

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