# Conditional iterator?
**URL:** https://discourse.julialang.org/t/conditional-iterator/40735
**Category:** New to Julia
**Created:** [June 4, 2020, 2:28pm UTC](https://discourse.julialang.org/t/conditional-iterator/40735 "2020-06-04T14:28:39Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)
#### Post date: [June 4, 2020, 2:28pm UTC](https://discourse.julialang.org/t/conditional-iterator/40735/1 "2020-06-04T14:28:39Z")
Is it possible to write something like this:
```julia
for (key, val) in dict if val != b
# do something
end
```
This would do the job
```julia
for (key, val) in dict
if val == b continue end
# do something
end
```
and this too
```julia
for (key, val) in dict if val != b
# do something
end end
```
but this looks funny.
After all you can write
```julia
[val for (key, val) in dict if val != b]
```
---
### Author:  [@anon94023334](https://discourse.julialang.org/u/anon94023334)
#### Post date: [June 4, 2020, 3:28pm UTC](https://discourse.julialang.org/t/conditional-iterator/40735/2 "2020-06-04T15:28:48Z")
```julia
for (k, v) in dict
v == b && continue
# do something
end
```
---
### Author:  [@non-Jedi](https://discourse.julialang.org/u/non-Jedi)
#### Post date: [June 4, 2020, 3:53pm UTC](https://discourse.julialang.org/t/conditional-iterator/40735/3 "2020-06-04T15:53:02Z")
If you really wanted something similar to this syntax, you could create a macro that transforms:
```julia
@when v != b, for (k, v) in dict
# do something
end
```
into:
```julia
for (k, v) in dict
if v != b
# do something
end
end
```
But in general, I think you’re better off writing it as shown by sbrombger above.
---
### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [June 4, 2020, 4:02pm UTC](https://discourse.julialang.org/t/conditional-iterator/40735/4 "2020-06-04T16:02:10Z")
Maybe
```julia
julia> d = Dict(1=>2, 2=>3, 3=>4)
Dict{Int64,Int64} with 3 entries:
2 => 3
3 => 4
1 => 2
julia> b = 3
3
julia> for (k,v) in Iterators.filter(kv -> kv.second != b, d)
@show k, v
end
(k, v) = (3, 4)
(k, v) = (1, 2)
```
---
### Author:  [@anon94023334](https://discourse.julialang.org/u/anon94023334)
#### Post date: [June 4, 2020, 4:30pm UTC](https://discourse.julialang.org/t/conditional-iterator/40735/5 "2020-06-04T16:30:45Z")
`Iterator.filter` is twice as slow for large dictionaries:
```julia
julia> @benchmark it(d, 3)
BenchmarkTools.Trial:
memory estimate: 48 bytes
allocs estimate: 2
--------------
minimum time: 1.532 s (0.00% GC)
median time: 1.534 s (0.00% GC)
mean time: 1.534 s (0.00% GC)
maximum time: 1.538 s (0.00% GC)
--------------
samples: 4
evals/sample: 1
julia> @benchmark noit(d, 3)
BenchmarkTools.Trial:
memory estimate: 16 bytes
allocs estimate: 1
--------------
minimum time: 839.276 ms (0.00% GC)
median time: 840.889 ms (0.00% GC)
mean time: 841.129 ms (0.00% GC)
maximum time: 843.754 ms (0.00% GC)
--------------
samples: 6
evals/sample: 1
```
```julia
julia> function it(d, b)
i = 0
for (k, v) in Iterators.filter(kv -> kv.second != b, d)
i += 1
end
i
end
julia> function noit(d, b)
i = 0
for (k, v) in d
v == b && continue
i += 1
end
i
end
```
---
### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [June 4, 2020, 5:26pm UTC](https://discourse.julialang.org/t/conditional-iterator/40735/6 "2020-06-04T17:26:12Z")
> [@anon94023334](#):
>
> `Iterator.filter` is twice as slow for large dictionaries:
The title said “conditional iterator” so I assumed that an iterator was desired.