# New to Julia

**URL:** https://discourse.julialang.org/c/first-steps/8.md?page=9

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

**Page:** 10

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## [How to debug incomplete precompilation](https://discourse.julialang.org/t/how-to-debug-incomplete-precompilation/132222)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 12\
**Last updated:** [September 9, 2025, 4:43pm UTC](https://discourse.julialang.org/t/how-to-debug-incomplete-precompilation/132222 "2025-09-09T16:43:20Z")

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I am having a problem that more or less every time I start Julia I run into precompilations that take ages (I can literally have hours each day where Julia is unavailable due to this). When I do using MyPackage I get a …

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## [What does the "?" next to a package name during precompilation mean](https://discourse.julialang.org/t/what-does-the-next-to-a-package-name-during-precompilation-mean/132221)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 2\
**Last updated:** [September 9, 2025, 9:14am UTC](https://discourse.julialang.org/t/what-does-the-next-to-a-package-name-during-precompilation-mean/132221 "2025-09-09T09:14:21Z")

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Figure this probably means something and it is probably something that one should know. When precompiling, sometimes there are “?” next to package name. What exactly do these ones mean? E.g. like hre: Progress \[=====…

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## [Do you need to recompile a package when you modify non-src files](https://discourse.julialang.org/t/do-you-need-to-recompile-a-package-when-you-modify-non-src-files/132019)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 4\
**Last updated:** [September 9, 2025, 8:53am UTC](https://discourse.julialang.org/t/do-you-need-to-recompile-a-package-when-you-modify-non-src-files/132019 "2025-09-09T08:53:34Z")

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I have problems with packages getting recompiled all the time, and I am trying to debug some of the cases (this has also happened just be restarting Julia, so there are difinitely cases where it does re-precompile when i…

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## [Automatic differentiation of loglikelihood function. Am I doing it right?](https://discourse.julialang.org/t/automatic-differentiation-of-loglikelihood-function-am-i-doing-it-right/132157)

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**Author:** [@giovannitinervia9](https://discourse.julialang.org/u/giovannitinervia9)\
**Replies:** 5\
**Last updated:** [September 8, 2025, 3:56pm UTC](https://discourse.julialang.org/t/automatic-differentiation-of-loglikelihood-function-am-i-doing-it-right/132157 "2025-09-08T15:56:15Z")

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Hi everyone! I’m a statistician and R user taking my first steps with Julia. I have extensive experience with R, and this summer I spent my free time reimplementing the R package gamlss as a personal exercise. Julia has…

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## [Help setting a filter that can return missing or non-missing values](https://discourse.julialang.org/t/help-setting-a-filter-that-can-return-missing-or-non-missing-values/132181)

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**Author:** [@Snowy](https://discourse.julialang.org/u/Snowy)\
**Replies:** 4\
**Last updated:** [September 8, 2025, 2:44pm UTC](https://discourse.julialang.org/t/help-setting-a-filter-that-can-return-missing-or-non-missing-values/132181 "2025-09-08T14:44:27Z")

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Hi all, Is there no way to specifically filter for missing values in a DataFrame column that is compatible with filtering for non-missing values (e.g. so a single filter can loop through non-missing and missing?) Take …

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## [Trouble with Measurements.jl and Bessel Functions](https://discourse.julialang.org/t/trouble-with-measurements-jl-and-bessel-functions/4562)

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**Author:** [@Jason\_Kilpatrick](https://discourse.julialang.org/u/Jason_Kilpatrick)\
**Replies:** 7\
**Last updated:** [September 7, 2025, 4:02pm UTC](https://discourse.julialang.org/t/trouble-with-measurements-jl-and-bessel-functions/4562 "2025-09-07T16:02:47Z")

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I am using Measurements.jl for error propagation in my code and have come across an error when trying to use it with a Bessel function with a complex input. This works using Measurements x = 1 ± 0.5 y = besselk(1. , x…

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## [What does the parser think this invalid construction means?](https://discourse.julialang.org/t/what-does-the-parser-think-this-invalid-construction-means/132155)

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**Author:** [@rcomm](https://discourse.julialang.org/u/rcomm)\
**Replies:** 10\
**Last updated:** [September 7, 2025, 2:00pm UTC](https://discourse.julialang.org/t/what-does-the-parser-think-this-invalid-construction-means/132155 "2025-09-07T14:00:46Z")

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I discovered today that this line: if \<cond expr\>: return true; else return false; end always returns true, whatever the value of x. The behaviour is the same in the REPL and in functions. I admit I thought that the …

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## [Simple FFT project performance](https://discourse.julialang.org/t/simple-fft-project-performance/132150)

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**Author:** [@agascoig](https://discourse.julialang.org/u/agascoig)\
**Replies:** 2\
**Last updated:** [September 7, 2025, 6:20am UTC](https://discourse.julialang.org/t/simple-fft-project-performance/132150 "2025-09-07T06:20:05Z")

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Hello! I am trying to do a simple FFT library just for fun, and not really for the highest performance. I am trying to write the code very transparently. If you want to look… (I can tell you that reverse engineerin…

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## [Media / Numerical solving for 1D thermal modeling with Modelingtoolkit](https://discourse.julialang.org/t/media-numerical-solving-for-1d-thermal-modeling-with-modelingtoolkit/131985)

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**Author:** [@junsin0106](https://discourse.julialang.org/u/junsin0106)\
**Replies:** 1\
**Last updated:** [September 6, 2025, 11:15pm UTC](https://discourse.julialang.org/t/media-numerical-solving-for-1d-thermal-modeling-with-modelingtoolkit/131985 "2025-09-06T23:15:16Z")

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Hello everyone, I’m a master’s course student just starting with Julia and ModelingToolkit. I have a few questions for those experienced in modeling and simulating thermal systems (like Vapor Compression Cycles or ORCs)…

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## [VSCodeServer problem](https://discourse.julialang.org/t/vscodeserver-problem/131983)

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**Author:** [@rcomm](https://discourse.julialang.org/u/rcomm)\
**Replies:** 1\
**Last updated:** [September 5, 2025, 2:33am UTC](https://discourse.julialang.org/t/vscodeserver-problem/131983 "2025-09-05T02:33:10Z")

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I am a new user struggling to make Julia work as intended. I have installed Julia and VS Code on to my Win10 laptop. I found winget won’t work - message is that it won’t run, although I can find it at multiple places o…

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## [1D Heat exchanger model with Dyad](https://discourse.julialang.org/t/1d-heat-exchanger-model-with-dyad/132009)

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**Author:** [@junsin0106](https://discourse.julialang.org/u/junsin0106)\
**Replies:** 6\
**Last updated:** [September 4, 2025, 1:41am UTC](https://discourse.julialang.org/t/1d-heat-exchanger-model-with-dyad/132009 "2025-09-04T01:41:20Z")

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Hello, I’m looking for examples of building a dynamic heat exchanger model in Dyad. I have seen some examples with TwoPort fluid models where mdot is the flow variable. My goal is to create a custom connector that inclu…

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## [OpenModelica with Julia SCIML application](https://discourse.julialang.org/t/openmodelica-with-julia-sciml-application/132066)

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**Author:** [@Dharani\_sree\_G](https://discourse.julialang.org/u/Dharani_sree_G)\
**Replies:** 2\
**Last updated:** [September 3, 2025, 11:47am UTC](https://discourse.julialang.org/t/openmodelica-with-julia-sciml-application/132066 "2025-09-03T11:47:27Z")

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I’m working on OpenModelica with Julia for one of my SCIML application. I’m unable to display the animation of my multibody physics model\_res.mat in my Julia application. Is there any package to support this

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## [Using Julia autodiff code from python with JAX](https://discourse.julialang.org/t/using-julia-autodiff-code-from-python-with-jax/132062)

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**Author:** [@gpxl](https://discourse.julialang.org/u/gpxl)\
**Replies:** 11\
**Last updated:** [September 2, 2025, 7:34pm UTC](https://discourse.julialang.org/t/using-julia-autodiff-code-from-python-with-jax/132062 "2025-09-02T19:34:01Z")

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I have a pretty basic question. I am a scientist who is new to Julia (hence the category I am posting this in), but interested in learning more both out of personal curiosity as well as the possible benefits for my own w…

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## [Precipitates in a 3D matrix](https://discourse.julialang.org/t/precipitates-in-a-3d-matrix/132002)

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**Author:** [@ES\_VI](https://discourse.julialang.org/u/ES_VI)\
**Replies:** 6\
**Last updated:** [September 2, 2025, 5:15am UTC](https://discourse.julialang.org/t/precipitates-in-a-3d-matrix/132002 "2025-09-02T05:15:56Z")

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Hi Everyone! I am trying to plot my data (4 columns x,y,z,composition) which when plotted in MATLAB looks like the figure attached. I tried other opensource tools like GNUPLOT and Octave. But those show the precipita…

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## [On formatting the display of integer arrays](https://discourse.julialang.org/t/on-formatting-the-display-of-integer-arrays/132023)

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**Author:** [@rcomm](https://discourse.julialang.org/u/rcomm)\
**Replies:** 6\
**Last updated:** [September 1, 2025, 5:48pm UTC](https://discourse.julialang.org/t/on-formatting-the-display-of-integer-arrays/132023 "2025-09-01T17:48:14Z")

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I do combinatorial work which generates arrays containing small integers. Some arrays are large, so to reduce memory footprint all calculations are done in UInt8. Part of the analysis is to visually scan displays of se…

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## [Performance implications of computations in keyword arguments](https://discourse.julialang.org/t/performance-implications-of-computations-in-keyword-arguments/131977)

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**Author:** [@loisel](https://discourse.julialang.org/u/loisel)\
**Replies:** 9\
**Last updated:** [September 1, 2025, 11:54am UTC](https://discourse.julialang.org/t/performance-implications-of-computations-in-keyword-arguments/131977 "2025-09-01T11:54:19Z")

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Long story short, I’m putting my entire function into default values of keyword arguments, and I want to know if this is bad. I’m working on a Julia package to solve PDEs. The “driver code” of such solvers often has a z…

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## [Failure to download artifact: CUDA\_Compiler](https://discourse.julialang.org/t/failure-to-download-artifact-cuda-compiler/131580)

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**Author:** [@mukund-gupta](https://discourse.julialang.org/u/mukund-gupta)\
**Replies:** 1\
**Last updated:** [September 1, 2025, 11:19am UTC](https://discourse.julialang.org/t/failure-to-download-artifact-cuda-compiler/131580 "2025-09-01T11:19:14Z")

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Hi everyone, I am new to CUDA.jl and am receiving the following error issues when performing using CUDA on a GPU node of a Linux cluster. Precompiling CUDA... 22064.9 ms ✓ InvertedIndices 22158.5 ms ✓ LaTeXString…

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## [Understanding random numbers in a GPU kernel](https://discourse.julialang.org/t/understanding-random-numbers-in-a-gpu-kernel/131771)

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**Author:** [@jwtkeeble](https://discourse.julialang.org/u/jwtkeeble)\
**Replies:** 4\
**Last updated:** [September 1, 2025, 11:15am UTC](https://discourse.julialang.org/t/understanding-random-numbers-in-a-gpu-kernel/131771 "2025-09-01T11:15:41Z")

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Hi All, I’m trying to understand the use of random numbers inside CUDA kerrnels in Julia. Below I have a simple script to estimate pi, but I have a few questions regarding its implementation. Is my implementation of r…

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## [Trying to adapt the initial coin-flip example on RxInfer to model a weighted die](https://discourse.julialang.org/t/trying-to-adapt-the-initial-coin-flip-example-on-rxinfer-to-model-a-weighted-die/131960)

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**Author:** [@B\_S](https://discourse.julialang.org/u/B_S)\
**Replies:** 2\
**Last updated:** [September 1, 2025, 10:23am UTC](https://discourse.julialang.org/t/trying-to-adapt-the-initial-coin-flip-example-on-rxinfer-to-model-a-weighted-die/131960 "2025-09-01T10:23:14Z")

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Hi all, I’m completely new to Julia and I apologize if this is a naive question, but I have been attempting to model a weighted die using RxInfer. I’ve followed the same structure as the coin\_toss example provide in the…

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## [GLMakie: Create specify point color](https://discourse.julialang.org/t/glmakie-create-specify-point-color/131971)

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**Author:** [@BananaMaster3](https://discourse.julialang.org/u/BananaMaster3)\
**Replies:** 4\
**Last updated:** [August 31, 2025, 8:40am UTC](https://discourse.julialang.org/t/glmakie-create-specify-point-color/131971 "2025-08-31T08:40:06Z")

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I have this code that graphs a scatterplot of points based off their position in the list points, then each frame runs a function to update their position and then graphs them again. How can I specify the point’s color w…

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## [I want Best Practices for Working With Python & Julia Together](https://discourse.julialang.org/t/i-want-best-practices-for-working-with-python-julia-together/131700)

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**Author:** [@Olivia](https://discourse.julialang.org/u/Olivia)\
**Replies:** 16\
**Last updated:** [August 29, 2025, 5:58pm UTC](https://discourse.julialang.org/t/i-want-best-practices-for-working-with-python-julia-together/131700 "2025-08-29T17:58:04Z")

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Hi everyone, I am enjoying how fast & expressive it feels compared to some other languages I have used before. I still rely a lot on Python for certain libraries & workflows. I have been exploring ways to combine the t…

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## [Is it possible to define '+' operator for string as '\*' do for them?](https://discourse.julialang.org/t/is-it-possible-to-define-operator-for-string-as-do-for-them/131835)

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**Author:** [@psalm1750](https://discourse.julialang.org/u/psalm1750)\
**Replies:** 12\
**Last updated:** [August 26, 2025, 1:29pm UTC](https://discourse.julialang.org/t/is-it-possible-to-define-operator-for-string-as-do-for-them/131835 "2025-08-26T13:29:30Z")

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I’d like to use ‘+’ operator for string concatenation. but it is ‘\*’ in Julia. If possible I’d like to define ‘+’ as alias of ‘\*’ if opland are strings. because some insufficient definition cause some side effect. Th…

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## [Parameter estimation in mathematical models of common functions (sine, cos, exp and other special functions)](https://discourse.julialang.org/t/parameter-estimation-in-mathematical-models-of-common-functions-sine-cos-exp-and-other-special-functions/130325)

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**Author:** [@Geegee](https://discourse.julialang.org/u/Geegee)\
**Replies:** 15\
**Last updated:** [August 28, 2025, 10:25am UTC](https://discourse.julialang.org/t/parameter-estimation-in-mathematical-models-of-common-functions-sine-cos-exp-and-other-special-functions/130325 "2025-08-28T10:25:44Z")

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Hello all glad to have arrived here. I have recently picked up Julia, but am quite excited about it! I have many data sets that follow the same model but the parameters change widely from dataset to dataset. In our la…

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## [Mapping over multidimensional array with eachslice](https://discourse.julialang.org/t/mapping-over-multidimensional-array-with-eachslice/131880)

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**Author:** [@Geegee](https://discourse.julialang.org/u/Geegee)\
**Replies:** 5\
**Last updated:** [August 27, 2025, 4:55pm UTC](https://discourse.julialang.org/t/mapping-over-multidimensional-array-with-eachslice/131880 "2025-08-27T16:55:10Z")

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I have a data opject Array{Float64, 3} where I want to map 2nd and 3rd dimension a function that accepts some static arguments and takes a Vector{Float64} from the data object. I tried to do this with eachslice(data, …

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## [What is the Julia equivalent of Rust Option\<T\>?](https://discourse.julialang.org/t/what-is-the-julia-equivalent-of-rust-option-t/122134)

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**Author:** [@world-peace](https://discourse.julialang.org/u/world-peace)\
**Replies:** 18\
**Last updated:** [August 27, 2025, 11:58am UTC](https://discourse.julialang.org/t/what-is-the-julia-equivalent-of-rust-option-t/122134 "2025-08-27T11:58:51Z")

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I read a few times about different ways in which Julia can represent optional wrapped types for return values. I am fairly confident I have seen this suggested before return type: Union{T, Nothing} # usage: return noth…

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## [Latexify/Catalyst introduces extra exponent - issue with mm and hill?](https://discourse.julialang.org/t/latexify-catalyst-introduces-extra-exponent-issue-with-mm-and-hill/131819)

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**Author:** [@orkun\_soyer](https://discourse.julialang.org/u/orkun_soyer)\
**Replies:** 6\
**Last updated:** [August 26, 2025, 2:54pm UTC](https://discourse.julialang.org/t/latexify-catalyst-introduces-extra-exponent-issue-with-mm-and-hill/131819 "2025-08-26T14:54:08Z")

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‘‘‘ ppGppSys1 = @reaction\_network begin kin, ∅ --\> G6P hill(G6P,v01,k01,1), G6P → F6P end odesys = convert(ODESystem, ppGppSys1; combinatoric\_ratelaws=false, remove\_conserved = true) latexif…

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## [Using PyCall with a non default Julia managed Conda Environment](https://discourse.julialang.org/t/using-pycall-with-a-non-default-julia-managed-conda-environment/131842)

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**Author:** [@LouisPauchet](https://discourse.julialang.org/u/LouisPauchet)\
**Replies:** 1\
**Last updated:** [August 25, 2025, 1:50pm UTC](https://discourse.julialang.org/t/using-pycall-with-a-non-default-julia-managed-conda-environment/131842 "2025-08-25T13:50:06Z")

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Hi Julia Community, I’m working on a project where I want to use PyCall, but I’d like to avoid the default Julia-managed Conda environment. Instead, I want to specify a custom environment. Here’s what I’m trying to achi…

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## [Null initialisation for a loop that appends vectors](https://discourse.julialang.org/t/null-initialisation-for-a-loop-that-appends-vectors/131754)

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**Author:** [@rcomm](https://discourse.julialang.org/u/rcomm)\
**Replies:** 14\
**Last updated:** [August 24, 2025, 5:35pm UTC](https://discourse.julialang.org/t/null-initialisation-for-a-loop-that-appends-vectors/131754 "2025-08-24T17:35:48Z")

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In Matlab, it is common to initialise a loop like this: x = ; for i = 1:n; x = \[x; another numerical row vector (of fixed length L)\]; end This creates a matrix of size \[n,L\]. It works regardless of chosen length L. W…

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## [One thread concurrency: realized in REPL, but failed in a function](https://discourse.julialang.org/t/one-thread-concurrency-realized-in-repl-but-failed-in-a-function/131621)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 17\
**Last updated:** [August 20, 2025, 12:20pm UTC](https://discourse.julialang.org/t/one-thread-concurrency-realized-in-repl-but-failed-in-a-function/131621 "2025-08-20T12:20:35Z")

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I did a test on the concurrency using @spawn, and find what the title suggests. I don’t know where is the twist. Here are my code import Base.Threads.@spawn Threads.nthreads() # use only one thread in this test s(x) = …

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## [Include c files while building Julia](https://discourse.julialang.org/t/include-c-files-while-building-julia/131717)

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**Author:** [@gitboy16](https://discourse.julialang.org/u/gitboy16)\
**Replies:** 0\
**Last updated:** [August 19, 2025, 7:54pm UTC](https://discourse.julialang.org/t/include-c-files-while-building-julia/131717 "2025-08-19T19:54:27Z")

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Hi, I know that it is possible to include some custom julia code in userimg.jl while building Julia. I was wondering if it is possible to also include C code that gets automatically compiled during the build process of…

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