# Using @printf to generate strings from format in Variable (maybe even in older Julia versions)
**URL:** https://discourse.julialang.org/t/using-printf-to-generate-strings-from-format-in-variable-maybe-even-in-older-julia-versions/76337
**Category:** General Usage
**Created:** [February 13, 2022, 9:36am UTC](https://discourse.julialang.org/t/using-printf-to-generate-strings-from-format-in-variable-maybe-even-in-older-julia-versions/76337 "2022-02-13T09:36:52Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@kellertuer](https://discourse.julialang.org/u/kellertuer)
#### Post date: [February 13, 2022, 9:36am UTC](https://discourse.julialang.org/t/using-printf-to-generate-strings-from-format-in-variable-maybe-even-in-older-julia-versions/76337/1 "2022-02-13T09:36:52Z")
I am struggling a little bit with how to use `@printf` within my code (maybe even functioning in Julia 1.4).
Consider the following minimal example, where I have a stream and the format given in some variables (in the concrete examples fields of a struct)
```julia
using Printf
io = stdout
f = "A %f"
@printf io "A %f" 1.0 # works
@printf io f 1.0 # does not work
```
On Julia 1.7 (and 1.6 but not earlier) I can do
```julia
Printf.format(io, Printf.Format(f), 1.0)
```
But this does neither work on Julia 1.4 or 1.5 – which – if possible – I would like to further support for sure. Any ideas how to get this last line work with `@printf` directly (or a similar idea) ?
---
### Author:  [@ctkelley](https://discourse.julialang.org/u/ctkelley)
#### Post date: [February 13, 2022, 12:43pm UTC](https://discourse.julialang.org/t/using-printf-to-generate-strings-from-format-in-variable-maybe-even-in-older-julia-versions/76337/2 "2022-02-13T12:43:34Z")
This works for me. It does not work without interpolating `f` or without the `@eval`
```julia
julia> @eval @printf io $f 1.0
A 1.000000
```
I do not understand this as metaprogramming is far above my pay grade. I figured this out by trial and error and randomly poking around in the manual. Tested on 1.7.2. I think it’s been working for me since 1.3.
---
### Author:  [@kellertuer](https://discourse.julialang.org/u/kellertuer)
#### Post date: [February 14, 2022, 4:11pm UTC](https://discourse.julialang.org/t/using-printf-to-generate-strings-from-format-in-variable-maybe-even-in-older-julia-versions/76337/3 "2022-02-14T16:11:56Z")
Maybe you are right and this is even the only way to got – then (I think) I might bump dependency to Julia 1.6 just to be safe and not use eval. I checked and your solution does work on 1.4 though.
---
### Author:  [@johnmyleswhite](https://discourse.julialang.org/u/johnmyleswhite)
#### Post date: [February 14, 2022, 4:18pm UTC](https://discourse.julialang.org/t/using-printf-to-generate-strings-from-format-in-variable-maybe-even-in-older-julia-versions/76337/4 "2022-02-14T16:18:46Z")
This not working is entirely to be expected from `@printf` being a macro – it depends on the variable being named `f`, but not on the value associated with `f`.
This definitely seems like a case where you want the functionality, but without the limits of the macro. The easiest thing is to impose the version requirements or to backport logic manually for yourself.
---
### Author:  [@kellertuer](https://discourse.julialang.org/u/kellertuer)
#### Post date: [February 15, 2022, 9:06pm UTC](https://discourse.julialang.org/t/using-printf-to-generate-strings-from-format-in-variable-maybe-even-in-older-julia-versions/76337/5 "2022-02-15T21:06:51Z")
Since I do also not see a way avoiding eval, it seems to be reasonable to set the lower bound to the current LTS, yes.