Technology Tales

Avoiding errors caused by missing Julia packages when running code on different computers

15th September 2024

As part of an ongoing move to multi-location working, I am sharing scripts and other artefacts via GitHub. This includes Julia programs that I have. That has led me to realise that a bit of added automation would help iron out any package dependencies that arise. Setting up things as projects could help, yet that feels a little too much effort for what I have. Thus, I have gone for adding extra code to check on and install any missing packages instead of having failures.

For adding those extra packages, I instate the Pkg package as follows:

import Pkg

While it is a bit hackish, I then declare a single array that lists the packages to be checked:

pkglits =["HTTP", "JSON3", "DataFrames", "Dates", "XLSX"]

After that, there is a function that uses a try catch construct to find whether a package exists or not, using the inbuilt eval macro to try a using declaration:

tryusing(pkgsym) = try
@eval using $pkgsym
return true
catch e
return false
end

The above function is called in a loop that both tests the existence of a package and, if missing, installs it:

for i in 1:length(pkglits)
rslt = tryusing(Symbol(pkglits[i]))
if rslt == false
Pkg.add(pkglits[i])
end
end

Once that has completed, using the following line to instate the packages required by later processing becomes error free, which is what I sought:

using HTTP, JSON3, DataFrames, Dates, XLSX