There are several command line incantations that I have had to look up at least a dozen times. I'm compiling a handy cheat sheet of them here.

These commands all work on my Mac, in the Terminal app running the shell zsh. I think most of them are directly portable to bash, but some will have small differences.

To drill deeper on any of these run man <command>. I find the examples section at the end most helpful.

Finding a string in Python files

grep -r --include \*.py 'string I am looking for' .

• grep finds strings
• -r drills down into directories recursively
• --include \*.py only checks files whose names end in .py
• 'string I am looking for' is the string to look for
• . signals to start looking in the current directory

Find files by name

find . -name '*partial_name*'

• find finds files and directories recursively
• . says to start in the current directory and work down
• -name '*partial_name*' is an instruction to find anything that has the string "partial_name" anywhere in its name.

Find and replace all occurrences of a string in a directory's Python files

sed -i '.bak' -e 's/old string/new string/g' *.py

• sed (stream editor) is a command to modify text
• -i '.bak' creates a backup copy of every modified file, using the extension .bak. If you want to live dangerously you can skip backups by specitying -i ''.
• -e instructs it to execute the command that follows
• 's/old string/new string/g' says to swap (s) the string old string for the string new string everywhere in the file, even if it occurs multiple times on the same line (g)
• *.py says to do this for all Python files in the directory.