10 Julia Recipes You Can't Miss

a.Accept arbitray number of function arguments

function sum1(a, remaining...)
    sm = a + sum(remaining)
    println(sm)
end

sum1(1, 2, 3, 4,5)
sum1(1)
sum1(1,2,3)

b.You can search and replace a simple text pattern in a string using the replace() method.

stri = "I scream, you scream, we all scream for ice cream."
stri = replace(stri, "scream" => "cry")
println(stri)
stri = "I scream, you scream, we all scream for ice cream."
replace(stri, "scream"=>uppercase) #replace scream by SCREAM

c. Filtering a list based on some condition

temp = [56, 49, 50, 55, 53, 52, 60, 60, 42, 54]

# Only the elements that are greater than 50
filtered = [item for item in temp if item > 50]
print(filtered)

filtered = filter(>(50), temp)

filtered = filter(temp) do x
    x > 50
end

d.Unpack tuple to a list of variables

temp1 = (45, 51, 43, 49, 47)
a, b, c, d, e = temp1
print(a)
print(d)

stri = "Money"
c1, c2, c3, c4, c5 = stri

t = (a=1, b="hello", c = 3.14) #named tuple
(; a, c) = t; @show a; @show c; #a = 1,c = 3.14,b undefined

e.Dictionary comprehension in Julia

marks = Dict("Ram" => 60, "Shyam" => 33, "Manik" => 64,"Mani" => 76, "Hema" => 84)

more_than_55 = Dict(key => value for (key, value) in marks if value > 60)
println(more_than_55)

names = Set(["Ram", "Hema", "Mani","Manik"])
selected = Dict(key => value for (key, value) in marks if key in names)
println(selected)

f.Iterating in Reverse in Julia

for i in reverse(1:5)
  print(i)
end

r = reverse("Julia")
"ailuJ"

for i in 1:length(r)
  print(r[reverseind("Julia", i)])
end

g.Padding Strings in Julia

str = "Julia's syntax is good"
println(lpad(str, 40, '*'))
println(rpad(str, 40, '*'))

h.Return multiple values from a function

function retMultipleValues()
    v1,v2 = "India","Iran"
    return v1,v2
end

countries = retMultipleValues()
println(countries)

i. Creating and Writing to a Text File in Julia

fid = open("abc.txt", "x") #"x" flag ensures that the file is created only if it does not already exist. 
write(fid, "Hello Julia")
close(fid)

open("def.txt", "w") do fid #no need for close statement
    write(fid, "Hey")
end

#Read a text file line by line
for line in eachline("my_file.txt")
    print(line)
end

#most compact
foreach(println,eachline("my_file.txt"))

j. Parse date string to DateTime object

using Dates

dstr = "2023-07-03"
println(typeof(dstr))

date_time = DateTime(dstr, "yyyy-mm-dd")
println(date_time)
println(typeof(date_time))

New trick suggested by reviewers:
k. Make a 10-element vector of random named tuples

points = [(x=rand(), y=rand()) for i in 1:10]
distances = [sqrt(p.x^2 + p.y^2) for p in points if p.x > p.y]
#distances = [hypot(p.x , p.y) for p in points if p.x > p.y]

l. Unpacking of tuples of varying sizes (Julia version 1.9)

julia> a, b..., c = (1, 2, 3, 4)
(1, 2, 3, 4)

julia> a
1

julia> b
(2, 3)

julia> c
4

m. Convert a number array to string

julia> r = join([1,2,3.1], ", ")
"1.0, 2.0, 3.1"

n. Round a float to integer

julia> round(Int, 12.5) == Int(trunc(12.5))
true

o. To parse a binary string to integer

parse(Int, "1011", base=2)

p. To create a random binary string

 join(rand(['1','0'],10))

Top comments (10)

Petr Krysl • Aug 28

Re (i): I personally like this pattern (takes care of the closing automatically):

open("def.txt", "w") do fid
    write(fid, "Hey")
end

Vinod V • Aug 28

Updated in the blog

Edward Carney • Sep 14

In item k., correct use of hypot, to make it equivalent to the sqrt() method, is hypot(p.x, p.y).

The one with a '+' returns the absolute value of the argument.

Vinod V • Sep 15

Corrected

hungpham3112 • Aug 26

Can you check again the code format?

Vinod V • Aug 27 • Edited

Done. I have replaced single tilde by three tildes followed by Julia. Now formatting is OK. Tilde code block is available as a default option in forem. It is not working properly.