# Can't override method
**URL:** https://discourse.julialang.org/t/cant-override-method/86419
**Category:** General Usage
**Created:** [August 27, 2022, 7:36am UTC](https://discourse.julialang.org/t/cant-override-method/86419 "2022-08-27T07:36:47Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@jar1](https://discourse.julialang.org/u/jar1)
#### Post date: [August 27, 2022, 7:36am UTC](https://discourse.julialang.org/t/cant-override-method/86419/1 "2022-08-27T07:36:47Z")
I tried to pirate this method so it doesn’t throw but it is ignored and throws an error. What is wrong?
Julia 1.7.1, PrettyTables master
```julia
[08abe8d2] PrettyTables v1.3.1 `https://github.com/ronisbr/PrettyTables.jl.git#master
```
```julia
using PrettyTables
# Pirate this function to allow arbitrary alignment specifiers.
function PrettyTables._latex_alignment(s::Symbol)
if (s == :l) || (s == :L)
return "l"
elseif (s == :c) || (s == :C)
return "c"
elseif (s == :r) || (s == :R)
return "r"
else
# Allow arbitrary alignments.
return String(s)
end
end
function maketable(d)
pretty_table(d; tf=LatexTableFormat(), alignment=[:r,Symbol("d{5.5}")])
end
maketable((;a=[1,2,3], b=[10.1,20.2,30.3]))
#=
ERROR: Invalid LaTeX alignment symbol: d{5.5}.
Stacktrace:
[1] error(s::String)
@ Base ./error.jl:33
[2] _latex_alignment
@ ~/.julia/packages/PrettyTables/gNyx5/src/backends/latex/private.jl:58 [inlined]
[3] |>
@ ./operators.jl:966 [inlined]
[4] _latex_table_description(ptable::PrettyTables.ProcessedTable, vlines::Symbol, left_vline::String, mid_vline::String, right_vline::String, hidden_columns_at_end::Bool)
@ PrettyTables ~/.julia/packages/PrettyTables/gNyx5/src/backends/latex/private.jl:79
[5] _pt_latex(io::IOContext{Base.TTY}, pinfo::PrettyTables.PrintInfo; tf::LatexTableFormat, body_hlines::Vector{Int64}, highlighters::Tuple{}, hlines::Nothing, label::String, longtable_footer::Nothing, sortkeys::Bool, table_type::Nothing, vlines::Nothing, wrap_table::Bool, wrap_table_environment::Nothing)
@ PrettyTables ~/.julia/packages/PrettyTables/gNyx5/src/backends/latex/print.jl:109
[6] _pt(io::IO, data::PrettyTables.ColumnTable; alignment::Vector{Symbol}, backend::Val{:auto}, cell_alignment::Nothing, cell_first_line_only::Bool, compact_printing::Bool, formatters::Nothing, header::Tuple{Vector{Symbol}, Vector{String}}, header_alignment::Symbol, header_cell_alignment::Nothing, limit_printing::Bool, max_num_of_columns::Int64, max_num_of_rows::Int64, renderer::Symbol, row_names::Nothing, row_name_alignment::Symbol, row_name_column_title::String, row_number_alignment::Symbol, row_number_column_title::String, show_header::Bool, show_row_number::Bool, show_subheader::Bool, title::String, title_alignment::Symbol, kwargs::Base.Pairs{Symbol, LatexTableFormat, Tuple{Symbol}, NamedTuple{(:tf,), Tuple{LatexTableFormat}}})
@ PrettyTables ~/.julia/packages/PrettyTables/gNyx5/src/private.jl:411
[7] #_pretty_table#61
@ ~/.julia/packages/PrettyTables/gNyx5/src/private.jl:275 [inlined]
[8] #pretty_table#53
@ ~/.julia/packages/PrettyTables/gNyx5/src/print.jl:694 [inlined]
[9] maketable(d::NamedTuple{(:a, :b), Tuple{Vector{Int64}, Vector{Float64}}}) =#
```
---
### Author:  [@ikirill](https://discourse.julialang.org/u/ikirill)
#### Post date: [August 27, 2022, 8:20am UTC](https://discourse.julialang.org/t/cant-override-method/86419/2 "2022-08-27T08:20:26Z")
This looks correct to me, and I checked that it works with git and 1.8.0, and doesn’t work with 1.7.3 or 1.6.7, so it’s probably just a bug.
---
### Author:  [@digital\_carver](https://discourse.julialang.org/u/digital_carver)
#### Post date: [August 27, 2022, 8:21am UTC](https://discourse.julialang.org/t/cant-override-method/86419/3 "2022-08-27T08:21:17Z")
You’re missing an import line
```julia
julia> import PrettyTables._latex_alignment
```
---
### Author:  [@ikirill](https://discourse.julialang.org/u/ikirill)
#### Post date: [August 27, 2022, 8:28am UTC](https://discourse.julialang.org/t/cant-override-method/86419/4 "2022-08-27T08:28:55Z")
Invoking julia with `--compiled-modules=no` also fixes it.
> [@digital\_carver](#):
>
> You’re missing an import line
I do not think this is correct: [Modules · The Julia Language](https://docs.julialang.org/en/v1/manual/modules/#namespace-management)
> [@](#):
>
> If a name is qualified, then it is always accessible, and in case of a function, it can also have methods added to it by using the qualified name as the function name.
I have always used this `OtherModule.f(x) = ...` syntax without an import, especially when adding definitions to `Base.*` methods for custom types so that I don’t have to import them one by one explicitly.
---
### Author:  [@ederag](https://discourse.julialang.org/u/ederag)
#### Post date: [August 27, 2022, 8:33am UTC](https://discourse.julialang.org/t/cant-override-method/86419/5 "2022-08-27T08:33:28Z")
Indeed, `import` does not seem required.
It works well here in 1.7.3, in a fresh REPL session.
> **REPL sesssion**
>
> ```julia
> julia
>
> (@v1.7) pkg> activate --temp
>
> (jl_iOafTJ) pkg> add PrettyTables
>
> julia> using PrettyTables
>
> julia> function PrettyTables._latex_alignment(s::Symbol)
> if (s == :l) || (s == :L)
> return "l"
> elseif (s == :c) || (s == :C)
> return "c"
> elseif (s == :r) || (s == :R)
> return "r"
> else
> # Allow arbitrary alignments.
> return String(s)
> end
> end
>
> julia> function maketable(d)
> pretty_table(d; tf=LatexTableFormat(), alignment=[:r,Symbol("d{5.5}")])
> end
> maketable (generic function with 1 method)
>
> julia> maketable((;a=[1,2,3], b=[10.1,20.2,30.3]))
> maketable((;a=[1,2,3], b=[10.1,20.2,30.3]))
> \begin{table}
> \begin{tabular}{rd{5.5}}
> \hline\hline
> \textbf{a} & \textbf{b} \\
> \texttt{Int64} & \texttt{Float64} \\\hline
> 1 & 10.1 \\
> 2 & 20.2 \\
> 3 & 30.3 \\\hline\hline
> \end{tabular}
> \end{table}
>
> julia> versioninfo()
> Julia Version 1.7.3
>
> ```
It might be worth trying in a fresh session,
and maybe with `julia --startup-file=no`,
in case something in your startup.jl is interfering.
---
### Author:  [@digital\_carver](https://discourse.julialang.org/u/digital_carver)
#### Post date: [August 27, 2022, 8:36am UTC](https://discourse.julialang.org/t/cant-override-method/86419/6 "2022-08-27T08:36:49Z")
> [@ederag](#):
>
> It works well here in 1.7.3, in a fresh REPL session.
Yeah, in a fresh session it’s not a problem. If you’ve used it at least once already, even indirectly (by calling a function that ultimately calls this), then you need an explicit import. In general, it’s just safer to do it anyway, since you can’t be sure what’s been in your call chains so far.
---
### Author:  [@ikirill](https://discourse.julialang.org/u/ikirill)
#### Post date: [August 27, 2022, 8:50am UTC](https://discourse.julialang.org/t/cant-override-method/86419/7 "2022-08-27T08:50:51Z")
> [@digital\_carver](#):
>
> If you’ve used it at least once already, even indirectly (by calling a function that ultimately calls this), then you need an explicit import.
Julia explicitly allows you to override existing methods and handles the resulting method invalidations by itself.
> [@ederag](#):
>
> It works well here in 1.7.3, in a fresh REPL session.
Note that you changed from `PrettyTables#master` to `PrettyTables`. This should not affect how method overriding works, yet changes behaviour here.
---
### Author:  [@ederag](https://discourse.julialang.org/u/ederag)
#### Post date: [August 27, 2022, 10:08am UTC](https://discourse.julialang.org/t/cant-override-method/86419/8 "2022-08-27T10:08:27Z")
Indeed, with `PrettyTables#master` the behavior is exactly as you described.
Overwriting `PrettyTables._latex_alignment` _after_ a first call to `maketable` (which errors) fixes it.
But it might be better to `pkg> dev PrettyTables`, apply your fix, and file a PR when it works.
Yet I guess that we are now two interested in an explanation,
if someone knows what’s going on 🙂 .
---
### Author:  [@jar1](https://discourse.julialang.org/u/jar1)
#### Post date: [August 28, 2022, 9:46am UTC](https://discourse.julialang.org/t/cant-override-method/86419/9 "2022-08-28T09:46:26Z")
Can I force the piracy to take effect using eval or something? It is inconvenient to have to get an error before using the function so I would like to force it.
---
### Author:  [@rdeits](https://discourse.julialang.org/u/rdeits)
#### Post date: [August 28, 2022, 3:11pm UTC](https://discourse.julialang.org/t/cant-override-method/86419/10 "2022-08-28T15:11:16Z")
> [@digital\_carver](#):
>
> Yeah, in a fresh session it’s not a problem. If you’ve used it at least once already, even indirectly (by calling a function that ultimately calls this), then you need an explicit import
Not so! Here’s a fresh session in which I call `Base.:*`, then overwrite that method without ever using `import`.
```julia
julia> 2.0 * 2.0
4.0
julia> function Base.:*(x::Float64, y::Float64)
println("piracy!")
Base.mul_float(x, y)
end
julia> 2.0 * 2.0
piracy!
piracy!
4.0
```