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haskey

haskey(collection, key) -> Bool

Determine whether a collection has a mapping for a given key.

Examples

julia> dict = Dict(["one"=> 1, "two"=> 2, "three"=> 3])
       haskey(dict, "one") 
true

julia> dict = Dict(["one"=> 1, "two"=> 2, "three"=> 3])
       haskey(dict, "1") 
false

julia> dict = ["A"=>1, "B"=>2];

julia> haskey(dict, "A")
true

julia> haskey(dict, 1)
false

1. Check if a dictionary has a specific key:

   julia> dict = Dict("apple" => 1, "banana" => 2, "orange" => 3);
   julia> haskey(dict, "banana")
   true

   This example checks if the dictionary dict has the key "banana".

2. Verify if a tuple has a specific element:

   julia> tuple = ("apple", "banana", "orange");
   julia> haskey(tuple, "orange")
   true

   It checks if the tuple tuple contains the element "orange".

3. Handle cases where the key is not present:

   julia> dict = Dict("apple" => 1, "banana" => 2, "orange" => 3);
   julia> haskey(dict, "grape")
   false

   This example demonstrates that haskey returns false if the key is not present in the dictionary.

Common mistake example:

julia> dict = Dict("apple" => 1, "banana" => 2, "orange" => 3);
julia> haskey(dict, 2)
ERROR: MethodError: no method matching haskey(::Dict{String, Int64}, ::Int64)

In this example, the key provided is of a different type (Int64) than the keys in the dictionary (String). It's important to provide the correct key type to haskey to avoid such errors. Make sure the key type matches the key types in the collection.

See Also

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