# Newbie Syntax Help: Colon in Index Syntax ---\> sepal\_length\_column = iris\[:Sepal\_Length\]
**URL:** https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918
**Category:** General Usage
**Created:** [June 25, 2018, 2:42am UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918 "2018-06-25T02:42:22Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Eli\_Hughes](https://discourse.julialang.org/u/Eli_Hughes)
#### Post date: [June 25, 2018, 2:42am UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918/1 "2018-06-25T02:42:22Z")
Hello:
I need some help to a doc page for a particular syntax (keep in mind I am a c programmer…) I have seen code that looks like this:
sepal\_length\_column = iris[:Sepal\_Length]
In the case above, it was an example from the dataframes module. What is the syntax in the square brackets? It is being used like array interation but with a string. I have not seen this type of syntax in other languages. I have also seen in in the PyPlot library. here is an example:
ax[:spines][“top”]:set\_color # Remove the top axis boundary
In this case :spines looks like it is some sort of binding to a class member in matplotlib.
A pointer to what this syntax is called would be helpful.
Thanks.
---
### Author:  [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)
#### Post date: [June 25, 2018, 2:57am UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918/2 "2018-06-25T02:57:19Z")
the square bracket syntax `[]` is just shorthand for the function `getindex` defined in Base.
Think of a DataFrame as an array of arrays, each one for a column. Then they define new methods for the function `getindex` to have the desired behavior. You can do this too.
```julia
struct A
x::Vector
end
import Base.getindex
function getindex(a::A, n)
getindex(A.x, n)
end
x = ["here", "there", "everywhere"]
a = A(x)
a[1]
> "here"
```
---
### Author:  [@ssfrr](https://discourse.julialang.org/u/ssfrr)
#### Post date: [June 25, 2018, 4:56am UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918/3 "2018-06-25T04:56:08Z")
prefixing text with a colon gives a `Symbol`, e.g. `:foo`, `:bar`. The `Dataframes` package allows a `DataFrame` to be indexed with a `Symbol` to refer to the column with that name.
The `PyCall` package allows python libraries to be called from Julia code, but translates a `obj.field` in Python into `obj[:field]` in Julia. see the [usage section of the docs](https://github.com/JuliaPy/PyCall.jl#usage) for details.
also - please surround quoted code with back-ticks so it gets nice syntax highlighting and is displayed in a fixed-width font. Single backticks are for in-line code `like this`, and triple quotes are used for longer code:
```julia
like this
```
---
### Author:  [@Eli\_Hughes](https://discourse.julialang.org/u/Eli_Hughes)
#### Post date: [July 1, 2018, 6:09pm UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918/4 "2018-07-01T18:09:55Z")
Thanks for the replies. Very Helpful!
---
### Author:  [@nalimilan](https://discourse.julialang.org/u/nalimilan)
#### Post date: [July 1, 2018, 8:16pm UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918/5 "2018-07-01T20:16:43Z")
FWIW on Julia 0.7 one can also write `iris.Sepal_Length` instead.
---
### Author:  [@nalimilan](https://discourse.julialang.org/u/nalimilan)
#### Post date: [July 1, 2018, 8:17pm UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918/6 "2018-07-01T20:17:08Z")
FWIW on Julia 0.7 one can also write `iris.Sepal_Length` instead, which calls the `getproperty`/`setproperty!` functions.
---
### Author:  [@swissr](https://discourse.julialang.org/u/swissr)
#### Post date: [July 2, 2018, 8:45am UTC](https://discourse.julialang.org/t/newbie-syntax-help-colon-in-index-syntax-sepal-length-column-iris-sepal-length/11918/7 "2018-07-02T08:45:28Z")
There is a very good explanation about what is a _symbol_ on stackoverflow by Stefan Karpinski. Link: [What is a "symbol" in Julia? - Stack Overflow](https://stackoverflow.com/questions/23480722/what-is-a-symbol-in-julia).