# Environment Variables¶

Best practice holds that variables should be passed to graphs via environment variables. Doing this is important for keeping sensitive data out of the code - such as an API token or username and password used to access a database. Not only is this approach more secure, it also makes graphs more flexible by allowing adjustments for a variety of environments and contexts. Importantly, environment variables are also the means by-which arguments can be passed to graphs.

Note

This document is about using your own settings and configuration values. If you’re looking for bonobo’s builtin settings, also configurable using environment variables, please check Settings & Environment.

## Passing / Setting Environment Variables¶

Setting environment variables for your graphs to use can be done in a variety of ways and which one used can vary based-upon context. Perhaps the most immediate and simple way to set/override a variable for a given graph is simply to use the optional --env argument when running bonobo from the shell (bash, command prompt, etc). --env (or -e for short) should then be followed by the variable name and value using the syntax VAR_NAME=VAR_VALUE. Multiple environment variables can be passed by using multiple --env / -e flags (i.e. bonobo run --env FIZZ=buzz ... and bonobo run --env FIZZ=buzz --env Foo=bar ...). Additionally, in bash you can also set environment variables by listing those you wish to set before the bonobo run command with space separating the key-value pairs (i.e. FIZZ=buzz bonobo run ... or FIZZ=buzz FOO=bar bonobo run ...). Additionally, bonobo is able to pull environment variables from local ‘.env’ files rather than having to pass each key-value pair individually at runtime. Importantly, a strict ‘order of priority’ is followed when setting environment variables so it is advisable to read and understand the order listed below to prevent

The order of priority is from lower to higher with the higher “winning” if set:

1. default values
os.getenv("VARNAME", default_value) The user/writer/creator of the graph is responsible for setting these.
2. --default-env-file values
Specify file to read default env values from. Each env var in the file is used if the var isn’t already a corresponding value set at the system environment (system environment vars not overwritten).
3. --default-env values
Works like #2 but the default NAME=var are passed individually, with one key=value pair for each --default-env flag rather than gathered from a specified file.
4. system environment values
Env vars already set at the system level. It is worth noting that passed env vars via NAME=value bonobo run ... falls here in the order of priority.
5. --env-file values
Env vars specified here are set like those in #2 albeit that these values have priority over those set at the system level.
6. --env values
Env vars set using the --env / -e flag work like #3 but take priority over all other env vars.

## Examples¶

The Examples below demonstrate setting one or multiple variables using both of these methods:

# Using one environment variable via a --env or --defualt-env flag:
bonobo run csvsanitizer --env SECRET_TOKEN=secret123
bonobo run csvsanitizer --defaul-env SECRET_TOKEN=secret123

# Using multiple environment variables via -e (env) and --default-env flags:
bonobo run csvsanitizer -e SRC_FILE=inventory.txt -e DST_FILE=inventory_processed.csv
bonobo run csvsanitizer --default-env SRC_FILE=inventory.txt --default-env DST_FILE=inventory_processed.csv

# Using one environment variable inline (bash-like shells only):
SECRET_TOKEN=secret123 bonobo run csvsanitizer

# Using multiple environment variables inline (bash-like shells only):
SRC_FILE=inventory.txt DST_FILE=inventory_processed.csv bonobo run csvsanitizer

# Using an env file for default env values:
bonobo run csvsanitizer --default-env-file .env

# Using an env file for env values:
bonobo run csvsanitizer --env-file '.env.private'


## ENV File Structure¶

The file structure for env files is incredibly simple. The only text in the file should be NAME=value pairs with one pair per line like the below.

# .env

DB_USER='bonobo'
DB_PASS='cicero'


## Accessing Environment Variables from within the Graph Context¶

Environment variables, whether set globally or only for the scope of the graph, can be can be accessed using any of the normal means. It is important to note that whether set globally for the system or just for the graph context, environment variables are accessed by bonobo in the same way. In the example below the database user and password are accessed via the os module’s getenv function and used to get data from the database.

import os

import bonobo
from bonobo.config import use

DB_USER = os.getenv('DB_USER')
DB_PASS = os.getenv('DB_PASS')

@use('database')
def extract(database):
with database.connect(DB_USER, DB_PASS) as conn:
yield from conn.query_all()

graph = bonobo.Graph(
extract,
bonobo.PrettyPrinter(),
)


## Where to jump next?¶

We suggest that you go through the tutorial first.

Then, you can read the guides, either using the order suggested or by picking the chapter that interest you the most at one given moment: