what's the difference between (%%)bash and bang(!) - bash

Question

In jupyter notebook, following gcloud commands work with bang(!) but not with %%bash
import os
PROJECT = 'mle-1234'
REGION = 'us-central1'
BUCKET = 'mle-1234'
# for bash
os.environ['PROJECT'] = PROJECT
os.environ['BUCKET'] = BUCKET
os.environ['REGION'] = REGION
os.environ['TFVERSION'] = '1.14.0' # Tensorflow version
# Set GCP Project and Region
%%bash
gcloud config set project $PROJECT
gcloud config set compute/region $REGION
gcloud config list
I get this error message when I execute the last snippet above with %%bash
File "<ipython-input-16-f93912dbcc34>", line 3
gcloud config set project $[PROJECT]
^
SyntaxError: invalid syntax
However, project and region values get set with same lines of code but by removing %%bash and prefixing (!) with all gcloud commands.
# Set GCP Project and Region
!gcloud config set project $PROJECT
!gcloud config set compute/region $REGION
!gcloud config list
Result with using (!)
Updated property [core/project].
Updated property [compute/region].
[compute]
region = us-central1
zone = us-central1-a
[core]
account = my-service-account#mle-1234.iam.gserviceaccount.com
disable_usage_reporting = False
project = mle-1234
What could be the reason for this behavior?

Answer 1

%%bash
%%bash is considered part of the Built-in magic commands. Run cells with bash in a subprocess. This is a shortcut for %%script bash. You can combine code from multiple kernels into one notebook. For example:
%%HTML
%%python2
%%python3
%%ruby
%%perl
implementation:
%%bash
factorial()
{
if [ "$1" -gt "1" ]
then
i=`expr $1 - 1`
j=`factorial $i`
k=`expr $1 \* $j`
echo $k
else
echo 1
fi
}
input=5
val=$(factorial $input)
echo "Factorial of $input is : "$val
! command
Starting a code cell with a bang character, e.g. !, instructs jupyter to treat the code on that line as an OS shell command
!cat /etc/os-release | grep VERSION
Output:
VERSION="16.04 LTS (Xenial Xerus)"
VERSION_ID="16.04"
Answer: since you are using gcloud commands, Jupyter will interpret those as OS shell commands; and therefore, using !glcoud will work.