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))
q. Convert a 1 x n matrix (row matrix) to a vector
B = [1 2 3 4]
1×4 Matrix{Int64}:
1 2 3 4
julia> dropdims(B,dims=1)
4-element Vector{Int64}:
1
2
3
4
r. Convert a row vector to a column vector
B = [1 2 3 4]
1×4 Matrix{Int64}:
1 2 3 4
julia> permutedims(B)
4×1 Matrix{Int64}:
1
2
3
4
s. Check occurrence of a number in a vector
a = [1,2,3]
in(1,a) # true
t. The command splice! can be used to remove elements from an array by index
a = [1,2,3]
splice!(a,2)
a
[1,3]
u. Get all the permutations with replacement (Cartesian product)
colors = ['R','G']
n = 3
vec(Iterators.product(fill(colors, n)...) |> collect)
8-element Vector{Tuple{Char, Char, Char}}:
('R', 'R', 'R')
('G', 'R', 'R')
('R', 'G', 'R')
('G', 'G', 'R')
('R', 'R', 'G')
('G', 'R', 'G')
('R', 'G', 'G')
('G', 'G', 'G')
v. Raw string in julia
x = raw"C:/temp"
w. Ternary operator with short circuited &&
x = 3 > 2 && 7 #x = 7
x = 2 > 3 && 7 #x = false
x. List all the files in a foler
readdir(raw"C:\temp")
y. Walk through the directory including subfolders
for (root,fold,files) in walkdir(raw"C:\temp")
for f in fl
println(joinpath(d,f)) #print all full file paths (python os.walk)
end
end
z. Pretty print a matrix
julia> using DelimitedFiles
julia> a = rand(2,3);
julia> writedlm(stdout, a)
0.29272827910923105 0.7551746399784662 0.22809145708060086
0.9698016822675571 0.7551356902700419 0.740811475230424
aa. To get the indices of elements satisfying certain condition
indices = findall(x -> x < 0, -4:10)
ab. Import a package with a different name
import LinearAlgebra as la
ac. Delete an element from a list
filter!(!=(1), [1,0,1,2,4])
ad. Convert data type of any to float in matrix
A = Matrix{Any}(rand(2,2))
B = similar(A,Float64)
B .= A
ae. Find the type of a Julia variable
a = 2
typeof(a)
a isa Int64
eltype(a)
af. Convert IEEE 754 hexadecimal string to float
hexStr = Meta.parse(string("0b", bitstring(1.0f0)))
0x3f800000
reinterpret(Float32,hexStr)
1.0f0
ag. To get the first half of the elements in a vector
x = rand(1024)
y = x[1:end÷2] #y = x[1:512]
ah. To restart the julia shell
run(`$(Base.julia_cmd())`)
Top comments (10)
Re (i): I personally like this pattern (takes care of the closing automatically):
Updated in the blog
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.
Corrected
Can you check again the code format?
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.
Nice post!
I think what you mean is "backtick" (`). Tilda is ~.
Regards,
P
True
Take a note at index of code block
I n the source I have numbered it properly. Is this a bug in forem software? I have changed indexing.
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