# Dynamicly change the Base.show methods with using macro?
**URL:** https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665
**Category:** New to Julia
**Created:** [March 10, 2022, 5:04am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665 "2022-03-10T05:04:02Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Brian1](https://discourse.julialang.org/u/Brian1)
#### Post date: [March 10, 2022, 5:04am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665/1 "2022-03-10T05:04:02Z")
There is two methods showing Float64:
```julia
t1show(io,x::Float64)=begin
if x<1e-3
xshow=x/1e-4 |> x->round(2,digits=2)
print(io,string(xshow)*" bp")
else
print(io,string(x))
end
end
t2show(io,x::Float64)=print(io,string(x))
```
Sometimes I want using t1show to show Float64, I would run this code:
```julia
Base.show(io::IO,x::Float64)=t1show(io,x)
0.0004
"4 bp"
```
Othertimes, I would like to show Float64 with using t2show, then I have to run this code:
```julia
Base.show(io::IO,x::Float64)=t2show(io,x)
0.0004
0.0004
```
This is not convinient. So does there is a elegant way to get like this:
```julia
0.0004
0.0004
@somemacro t2show 0.0004
"4 bp"
0.0004
0.0004
```
---
### Author:  [@Brian1](https://discourse.julialang.org/u/Brian1)
#### Post date: [March 11, 2022, 8:07am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665/2 "2022-03-11T08:07:16Z")
Finally, I find a way to do it:
```julia
macro cshow(f,expr)
func=eval(f)
ft=methods(func)[1].sig.parameters[3]
return quote
Base.show(io::IO,a::$ft)=$func(io,a)
x=$expr
show(x)
Base.delete_method(methods(Base.show,(IO,$ft))[1])
end |>esc
end
@cshow t1show 0.0004
4 bp
0.0004
0.0004
```
---
### Author:  [@tomerarnon](https://discourse.julialang.org/u/tomerarnon)
#### Post date: [March 11, 2022, 8:40am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665/3 "2022-03-11T08:40:04Z")
Why not just call `t1show(0.0004)` when that’s what you want? What’s the advantage of the macro?
---
### Author:  [@Brian1](https://discourse.julialang.org/u/Brian1)
#### Post date: [March 11, 2022, 8:44am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665/4 "2022-03-11T08:44:34Z")
I use it in jupyter, when call t1show, it needs the parameter “io”.
---
### Author:  [@tomerarnon](https://discourse.julialang.org/u/tomerarnon)
#### Post date: [March 11, 2022, 8:48am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665/5 "2022-03-11T08:48:25Z")
You need to define `t1show(x) = t1show(stdout, x)`
---
### Author:  [@Brian1](https://discourse.julialang.org/u/Brian1)
#### Post date: [March 11, 2022, 9:33am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665/6 "2022-03-11T09:33:27Z")
I tried just now, This method has a problem, I have to define functions : `tshow(x::Float64) tshow(x::Vector)....`, this is not convnient.
---
### Author:  [@fredrikekre](https://discourse.julialang.org/u/fredrikekre)
#### Post date: [March 11, 2022, 10:49am UTC](https://discourse.julialang.org/t/dynamicly-change-the-base-show-methods-with-using-macro/77665/7 "2022-03-11T10:49:47Z")
You can define a fallback: `tshow(x::Any) = show(x)`.