# Global variables not accessible inside loop

**URL:** <https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711>\
**Category:** New to Julia\
**Created:** [April 3, 2019, 6:57pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711 "2019-04-03T18:57:50Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![iamsuddhasattwa](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/iamsuddhasattwa/32/7441_2.png) [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Post date:** [April 3, 2019, 6:57pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/1 "2019-04-03T18:57:50Z")

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I am trying to execute this simple lines of code, but keep getting an undef error, although I explicitly define my variable to be global.

> global t = 1;  
> for i in 1:10  
> t+=0.1;print(“\ni=”,i,“, t=”,t);  
> end

This gives

> ERROR: UndefVarError: t not defined  
> I am using Julia 1.1.0. Can you help me understand what I am doing wrong.

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**Author:** ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)\
**Post date:** [April 3, 2019, 7:01pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/2 "2019-04-03T19:01:26Z")

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You need `global t += 0.1` in the loop to modify a global.

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**Author:** ![jbrea](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jbrea/32/3879_2.png) [@jbrea](https://discourse.julialang.org/u/jbrea)\
**Post date:** [April 3, 2019, 7:01pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/3 "2019-04-03T19:01:47Z")

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The keyword `global` is at the wrong place.

```julia
t = 1;
for i in 1:100  
    global t += 0.1
    @show t i
end

```

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**Author:** ![jlperla](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jlperla/32/34332_2.png) [@jlperla](https://discourse.julialang.org/u/jlperla)\
**Post date:** [April 3, 2019, 7:15pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/4 "2019-04-03T19:15:03Z")

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If you are an introductory user, then I suggest for now either (1) using Jupyter for exploration, as it is more intuitive; or (2) wrap code with loops in functions if working in the console or top level scripts.

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**Author:** ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)\
**Post date:** [April 3, 2019, 7:30pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/5 "2019-04-03T19:30:48Z")

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Or just use the `global` keyword if you want to modify a global variable from inside a loop, function or other scope block.

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<div class="post-metadata">

**Author:** ![iamsuddhasattwa](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/iamsuddhasattwa/32/7441_2.png) [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Post date:** [April 4, 2019, 1:17pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/6 "2019-04-04T13:17:28Z")

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Thanks. I will reread the manual and try to understand why this works.

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**Author:** ![iamsuddhasattwa](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/iamsuddhasattwa/32/7441_2.png) [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Post date:** [April 4, 2019, 1:18pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/7 "2019-04-04T13:18:02Z")

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Thanks. I will try to get Jupyter.

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<div class="post-metadata">

**Author:** ![iamsuddhasattwa](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/iamsuddhasattwa/32/7441_2.png) [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Post date:** [April 4, 2019, 1:18pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/8 "2019-04-04T13:18:18Z")

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I will reread the manual and try to understand why this works. Thanks !

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<div class="post-metadata">

**Author:** ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)\
**Post date:** [April 4, 2019, 3:03pm UTC](https://discourse.julialang.org/t/global-variables-not-accessible-inside-loop/22711/9 "2019-04-04T15:03:18Z")

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4 posts were split to a new topic: [Installing IJulia](https://discourse.julialang.org/t/installing-ijulia/22755)