instructing f-string over format()

[Skaperen]

a lot of my scripts generate what is call "user data", which is usually a bash script to be run, for instances being launched in the AWS EC2 cloud. these have a lot of variable substitution in them. i have been using .format, but i think f-strings will do well in these. i used to code them as multi-line triple-quoted strings but that was difficult to use with .format() so i switched each line being a single call to a function named ud() with .format() in there. so instead of:

ud("#!/bin/bash")
ud("export JOB='{}'".format(job_id))
ud("mkdir '{}'".format(log_dir_name))
ud("exec &>'{}".format(log_file_name))
...
ud("aws s3 sync '{}' 's3://{}{}'".format(log_dir_name,bucket,s3_prefix))

i can do:

ud(f"""#!/bin/bash
export JOB='{job_id}'
mkdir '{log_dir_name}'
exec &>'log_file_name'
...
aws s3 sync '{log_dir_name}' 's3://{bucket}{s3_prefix}'
""")

this is one of the reasons i wanted to get 3.6 or 3.7 running system-wide on my old Ubuntu 16.04 system that had 3.5 system-wide. upgrading to a full fresh install of Xubuntu 18.04 got me several things i wanted, including f-strings for these scripts.

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i do expect to still use .format() in some other situations. but i do expect to migrate to only using f-strings for locally run scripts. stuff i make for others will use .format() for a very long time.