JuliaUsefulCommands.md

Julia Useful Commands and Code

Here is a collection of useful code that I've either found or made myself

Julia code quirks

Most of these quirks are very useful so it is good to know about them.

• When creating a function if you put a ! after the function name but before the inputs the function will be able to change the inputs otherwise they will be treated as immutable

Path management

Path management can be a pain to figure out so I'm adding everything I've learned about path management in Julia here.

• @__DIR__ and dirname(@__FILE__) both return an AbstractString

• The following for loop is kind of like globbing for files that end in a certain extension:

  for f in filter(x -> endswith(x, "jl"), readdir())
      println(f)
  end

• I find it very common to put a script in a folder and want to have the program "search" for a folder in parent folders until that folder is found. This is how I do that in a function.

  using FilePathsBase
  using Glob
  
  function find_edgelist_files(target_folder)
      """finds the directory with all of the edgelist files"""
      path = Path(dirname(@__FILE__))
      n = 0
      while true
          listDirs = [path_1 for path_1 in readdir(path) if isdir(path)]
          listDirsStem = [string(basename(path_1)) for path_1 in readdir(path) if isdir(path)]
          if target_folder in listDirsStem
              path = path / target_folder
              files = glob("*.csv", string(path))
              # break
              return files, path
          else
              path = parent(path)
          end
      end
  end
  
  target_folder = "author_subreddit_edgelists"
  find_edgelist_files(target_folder)

Dataframe related code

• Similar to the isin function in pandas where you filter a dataframe based on what is in another array or list of items

  df[ [x in [3,4] for x in df[:A]] ,:]

Random bits of useful code

• An easy way to time some function is to use the @elapsed macro, this will print the output in seconds that it took to run whatever you're evaluating