Clever Geek Handbook

Create a list of paired string values ​​in PowerShell

For a project I am doing, I need to check and see if a couple of lines are present in a line from a file.

I tried to use a hash table like this:

$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza'

$table = @{}

for ($i = 0; $i -lt $makes.Length; $i++)
{
    $table.Add($makes[$i], $models[$i])
}

This works well until I try to insert a duplicate make. I quickly discovered that hash tables do not accept duplicates.

So, is there a way to create a double list of strings in PowerShell? It's very easy to do this in C #, but I haven't found a way to achieve it in PowerShell.

+5


source to share


4 answers


With minimal changes to your code and logic:

$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza'

for ($i = 0; $i -lt $makes.Length; $i++){
    [array]$cars += New-Object psobject -Property @{
        make  = $makes[$i]
        model = $models[$i]

    }
}


This uses a custom psobject

cast to array to resolve +=

.

+4


source


Here's a way to avoid array concatenation (similar to Python's list comprehension syntax):



$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza'

$cars = 0..$makes.Length | ForEach-Object {
  [PSCustomObject] @{
    Make  = $makes[$_]
    Model = $models[$_]
  }
}
+4


source


You can use PSCustomObject

and just populate the list directly:

$cars = @(
    [pscustomobject]@{make = "Ferrari"; model="Enzo"}
    [pscustomobject]@{make = "Ford"; model="Focus"}
    [pscustomobject]@{make = "Peugeot"; model="206"}
    [pscustomobject]@{make = "Subaru"; model="Imprezza"}
)
+4


source


Note. The question asked - creating a list of value pairs regardless of duplicates - is most effectively answered by Bill Stewart's answer .
This answer focuses on a hash table solution that collects all models for a given brand into a single record and provides efficient search for models by brand.

You can still use a hash table - with its handy key-based searches - if you store all the models associated with a given brand as an array in each brand - by definition one single - entry :

# Note the duplicate 'VW' entry at the end.
$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru', 'VW'
# Corresponding models.
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza', 'Polo'

$table = [ordered] @{}; $i=0  # [ordered] (PSv3+) preserves the order of the keys
foreach($make in $makes) {
  # Add the model at hand to the make array of models.
  # The entry is created on demand as an array, due to [array]
  # (which creates an [object[]] array),
  # and for additional models the array is appended to.
  # You could also use [string[]], specifically.
  [array] $table[$make] += $models[$i++]
}

# Output the resulting hashtable
$table

This gives:

Name                           Value                                                                                                                                               
----                           -----                                                                                                                                               
Ferrari                        {Enzo}                                                                                                                                              
Ford                           {Focus}                                                                                                                                             
VW                             {Golf, Polo}                                                                                                                                        
Peugeot                        {206}                                                                                                                                               
Subaru                         {Impreza}

Note that the value VW

has 2 entries ( {...}

indicates that the value is an array).

To get this model (s) later, just use:

$vwModels = $table['VW']

To check if a given manufacturer / model pair is contained in the table:

$table[$make] -contains $model
+2


source






More articles:


All Articles