Introduction to the Julia programming language

10 Filesystem

The do syntax we saw earlier is helpful when using the open() function:

open("test.txt", "w") do f
    write(f, "This is a test.\n")
    write(f, "I repeat, this is a test.\n")
end

open("test.txt") do f
    for line in eachline(f)
        println("[$line]")
    end
end

[This is a test.]
[I repeat, this is a test.]

Alternatively, you can read the whole file into a string:

s = read("test.txt", String)

"This is a test.\nI repeat, this is a test.\n"

Reading a file from a URL

using CSV, HTTP, DataFrames
ENV["DATAFRAMES_ROWS"] = 6;

url = "https://www.physi.uni-heidelberg.de/~reygers/lectures/2021/ml/data/magic04_data.txt"

# Read the CSV file from the URL
response = HTTP.get(url)
df = CSV.read(IOBuffer(response.body), DataFrame)

19020×11 DataFrame

19014 rows omitted

Row	fLength	fWidth	fSize	fConc	fConc1	fAsym	fM3Long	fM3Trans	fAlpha	fDist	class
	Float64	Float64	Float64	Float64	Float64	Float64	Float64	Float64	Float64	Float64	String1
1	28.7967	16.0021	2.6449	0.3918	0.1982	27.7004	22.011	-8.2027	40.092	81.8828	g
2	31.6036	11.7235	2.5185	0.5303	0.3773	26.2722	23.8238	-9.9574	6.3609	205.261	g
3	162.052	136.031	4.0612	0.0374	0.0187	116.741	-64.858	-45.216	76.96	256.788	g
⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮	⋮
19018	75.4455	47.5305	3.4483	0.1417	0.0549	-9.3561	41.0562	-9.4662	30.2987	256.517	h
19019	120.513	76.9018	3.9939	0.0944	0.0683	5.8043	-93.5224	-63.8389	84.6874	408.317	h
19020	187.181	53.0014	3.2093	0.2876	0.1539	-167.312	-168.456	31.4755	52.731	272.317	h