# Creating Token with OAuth2
We can follow the documentation [here](https://fastapi.tiangolo.com/tutorial/security/oauth2-jwt/?h=oauth)
* First we will have to install the `python-jose` library
```python
pip install "python-jose[cryptography]"
```
* Next we will create a file called `oauth2.py` in the `app` folder
* In said file we will import the following:
```python
from jose import JWTError, jwt
```
* We will need to provide 3 things
* The Secret Key
* The Algorithm that we want to use
* The Expiration time of the token - if we do not provide this, the user is logged forever
```python
from jose import JWTError, jwt
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30
```
* Creating the JWT function and returning the token
```python
from jose import JWTError, jwt
from datetime import date, datetime, timedelta
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30
def create_access_token(data: dict):
# We do not want to modify the actual data, so we create a copy
to_encode = data.copy()
# We use the datetime.now() so we can update the time to expiry
expire = datetime.now() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
# to_encode is a dirctionary so we are updating this with the expiration time
to_encode.update({"exp": expire})
# Now as we have the data, we can return the JWT by using the .encode method
# and providing the data, the secret key, and the algorithm in the method
encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
return encoded_jwt
```
* Now that we can create the token, we will update this in the `auth.py` file
```python
from os import access
from fastapi import APIRouter, Depends, status, HTTPException, Response
from sqlalchemy.orm import Session
from .. import database, schemas, models, utils, oauth2
router = APIRouter(
tags=['Authentification']
)
@router.post('/login')
def login(user_credentials: schemas.UserLogin, db: Session = Depends(database.get_db)):
user = db.query(models.User).filter(models.User.email == user_credentials.email).first()
if not user:
raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=f"Invalid Credentials")
if not utils.verify(user_credentials.password, user.password):
raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=f"Invalid Credentials")
# REMEMBER:
# This is the data that we decide to put in the payload
# In this case we only care about the user_id
access_token = oauth2.create_access_token(data= {"user_id": user.id})
return {"access_token" : access_token,
"token_type": "bearer"
}
```
* If we use postman to see how the login works we should get the following data back:
```json
{
"access_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjo4LCJleHAiOjE2NjE1MjM1NDV9.W6JBT_5xf-OQIYBiXiH4ZXp2jpVLxl4AgPccChVx2Ic",
"token_type": "bearer"
}
```
{% hint style="info" %}
Now go to [jwt.io ](https://jwt.io/)and paste the token in there.
* This will automatically decode our JWT Token
{% endhint %}
