# Import Modules in Python

Reference: [Python Tutorial for Beginners 9: Import Modules and Exploring The Standard Library](https://youtu.be/CqvZ3vGoGs0?t=373)

Case 1: Assume we have two scripts which are placed in the same direcotry.
---

Decktop
│    my_module.py   
│    intro.py
└─ 

We can import `my_module` because it's in the same directory as our `intro.py`
---

### my_module.py ###
print('Imported my_module...')

test = 'Test String'

def find_index(to_search, target):
    '''Find the index of a value in a sequence'''
    for i, value in enumerate(to_search):
        if value == target:
            return i

    return -1

### intro.py ###
import my_module as mm

courses = ['History', 'Math', 'Physics', 'CompSci']

index = mm.find_index(courses, 'Math')

print(index) # 1

### Q: Why we can import that directly?
### A: Because the module path is in `python environment path`
- Python will look for modules in the `environment path`
- p.s. We can check this by print out the `sys.path`

### intro.py ###
import sys

print(sys.path)

import my_module as mm

courses = ['History', 'Math', 'Physics', 'CompSci']

index = mm.find_index(courses, 'Math')

print(index) # 1

### output of `sys.path`

['/Users/joe/Desktop', 
'/Users/joe/miniconda3/lib/python37.zip', 
'/Users/joe/miniconda3/lib/python3.7', 
'/Users/joe/miniconda3/lib/python3.7/lib-dynload',
'/Users/joe/miniconda3/lib/python3.7/site-packages']

#### So as you can see the 1st element of `sys.path list` is `/Users/joe/Desktop`

Case 2: Assume we have two scripts which aren't placed in the same direcotry.
---

Decktop
│ 
│   intro.py
│ 
└───my_modules
│   └─   my_module.py 
└─ 

## Method 1: Append the path of `my_module.py` before importing `my_module`

### intro.py ###
import sys
sys.path.append('/Users/joe/Desktop/my_modules')

courses = ['History', 'Math', 'Physics', 'CompSci']

from my_module import find_index

index = find_index(courses, 'Math')

print(index) # 1

### output of `sys.path`

['/Users/joe/Desktop',
'/Users/joe/miniconda3/lib/python37.zip',
'/Users/joe/miniconda3/lib/python3.7',
'/Users/joe/miniconda3/lib/python3.7/lib-dynload',
'/Users/joe/miniconda3/lib/python3.7/site-packages',
'/Users/joe/Desktop/my_modules']  # the path that we append.

#### So as you can see the last element of `sys.path list` is `/Users/joe/Desktop/my_modules`
#### So that's where and why python can find the `my_module.py`

### What is `sys.path`?
- This is the `list of directories` my machine where python looks for modules where we run an import
- The first value here is just the `directory where I'm currently running the script from` and the `my_module.py` that we're importing is within that directory also, so that's how it found it.

### Q: So what directories are added to this sys.path list?
### A: Directories are added in this order:
- First the directory containing the script that we're `currently running`.
- And next it adds directories listed in the `Python path environment variable`.
- And after the Python path it then adds the `standard library diectories`.
- And lastly, it adds the site packages directory for `third-party packages`.

### Drawbacks of adding environment path by `sys.path.append`
- This isn't the best looking approach, because we're appending this directory before our other imports.
- And also if we were to import our module and we had this maunally hard-coded in multiple locations.
- And we had to change all of those.

## Method 2: Change`Python Path Environment variables`
- p.s. Changing the environment variables is different on Mac and Windows, we're only going to show how change on Mac or linux.

### Step1: Open your terminal

### Step2: Edit the `.bash_profile`

nano ~/.bash_profile


### Step3: Add the path and finish~

export PYTHONPATH="/Users/joe/Desktop/my_modules"

p.s. no spaces between PYTHONPATH and "="

### Step4: Restart terminal or type the follow command in the terminal

source ./bash_profile

### Step5: Print out the `sys.path`

print(sys.path)

['', '/Users/joe/Desktop/my_modules',
'/Library/Frameworks/Python.framework/Versions/3.7/lib/python37.zip',
'/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7',
'/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/lib-dynload',
'/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages']

And we see the `'/Users/joe/Desktop/my_modules'` is in the `list`!

###### tags: `Python`