Calling and creating a function in python

Question

I'm fairly new to python (still in the first few chapters of an introductory book) and i was wondering, once i have defined a function and saved it in script mode, and i want to use it in another script do i have to define it the new program?

To clarify suppose a create a function multiplybyfive(x) which takes an input and x and returns 5x. Now suppose i create a program which uses multiplybyfive(x) in it, do i have to define it again in this new program or can i simply call it somehow?

[you can import it](https://docs.python.org/3/reference/import.html) look at the docs — John Ruddell, Oct 07 '15 at 18:43
Read this, it should help: http://stackoverflow.com/questions/20309456/how-to-call-a-function-from-another-file-in-python — idjaw, Oct 07 '15 at 18:44
Thanks, i tried this in the idle mode import multiplybyfive(x) and it came up with an error — Pavan Sangha, Oct 07 '15 at 18:44
you need a from. `from path/to/file import multiplybyfive` then later you can use it like this. `multiplybyfive(x)` — John Ruddell, Oct 07 '15 at 18:46
@ john Ruddell do i write it exactly how you have? I tried from path/to/file import multiplybyfive and it returns invalid syntax — Pavan Sangha, Oct 07 '15 at 18:48
@PavanSangha no. path/to/file is the location of your file. like if its on your desktop for mac then it would be like `/Users/computer_name/Desktop/math_file import multiplybyfive` where computer_name is the name of your computer and math_file is the name of the file that has your math function — John Ruddell, Oct 07 '15 at 18:53
@PavanSangha I would advise you to continue **reading the book**, rather than asking here. — Ajean, Oct 07 '15 at 18:55
I saved it in a file called multiply.py and i tried---------------------------------- from multiply import multiplybyfive Traceback (most recent call last): File "", line 1, in from multiply import multiplybyfive ImportError: No module named 'multiply' — Pavan Sangha, Oct 07 '15 at 18:55
I have a folder in my desktop of scripts of python programs which i have saved — Pavan Sangha, Oct 07 '15 at 18:57
ok what is the exact path to your desktop from the root folder? — John Ruddell, Oct 07 '15 at 18:57
@PavanSangha your desktop is a folder. it has a parent folder. you have to figure out what your parent folder is until you get to the root folder — John Ruddell, Oct 07 '15 at 20:50
ok, so the path according to your definition is favourites>>>desktop, so i guess the root folder is the favourites folder? — Pavan Sangha, Oct 07 '15 at 20:53

score 0 · Answer 1 · answered Oct 07 '15 at 18:48

0

You can import the python file which contains function multiplybyfive(x) into your new file.

For example, if you write multiplybyfive(x) in file mathfunction.py file. You can use it in a new program by

from mathfunction import multiplybyfive

x = 1
y = multiplybyfive(x)
print y

answered Oct 07 '15 at 18:48

Hao Lyu

176
1
5

Ok thanks, I've tried using that in IDLE mode but it doesn't work, does that just work for script mode? – Pavan Sangha Oct 07 '15 at 18:52
@PavanSangha you cant just copy paste an import. it has to be a folder path from your computer. look at where the folder is and figure out what your path is – John Ruddell Oct 07 '15 at 18:54

score 0 · Answer 2 · answered Oct 07 '15 at 18:50

Why would you want to define it again? Most languages don't work like this. Consider the following layout:

src:
|-- some_module_with_function_def.py
|-- some_other_module_to_call_function.py

You can have the function definition in some_module_with_function_def.py and you can then use it in some_other_module_to_call_function.py just by doing this:

from some_module_with_function_def import multiplybyfive

x = multiplybyfive(10)

Calling and creating a function in python

2 Answers2