Hash tables (dictionaries) in PowerShell - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a hash table in PowerShell?

A hash table is a collection of key-value pairs. It lets you store and quickly find data by using a unique key, like a labeled box for your information.

beginner

How do you create an empty hash table in PowerShell?

You create an empty hash table using @{} like this: <br>$myHash = @{}

beginner

How do you add a key-value pair to a hash table?

Use the syntax: <br>$hashTable["key"] = "value"<br>This adds or updates the value for the given key.

beginner

How do you access a value from a hash table by its key?

Use the key inside square brackets: <br>$value = $hashTable["key"]<br>This gets the value stored for that key.

beginner

What happens if you try to access a key that does not exist in a hash table?

PowerShell returns nothing (null). It does not cause an error, but you get no value back.

Which symbol is used to create a hash table in PowerShell?

A ()

B []

C {}

D @{}

The @{} syntax creates a hash table in PowerShell.

How do you add a new key 'Name' with value 'Alice' to a hash table $h?

A $h.Add('Name', 'Alice')

B $h['Name'] = 'Alice'

C $h.Name = 'Alice'

D $h->Name = 'Alice'

In PowerShell, you add or update a key-value pair using $h['Name'] = 'Alice'.

What does $h['Age'] return if 'Age' is not a key in $h?

A Null (no value)

B An error

C 0

D The string 'Age'

Accessing a missing key returns null, not an error.

How do you create a hash table with keys 'City' and 'Country' and values 'Paris' and 'France'?

A $h = @{City='Paris'; Country='France'}

B $h = ['City'='Paris', 'Country'='France']

C $h = {'City':'Paris', 'Country':'France'}

D $h = (City='Paris', Country='France')

The correct syntax uses @{} with semicolons separating key-value pairs.

Which of these is NOT a valid way to access a hash table value?

A $h['Key']

B $h.Key

C $h->Key

D $h.Get_Item('Key')

PowerShell does not use '->' to access hash table items.

Explain how to create, add to, and retrieve data from a hash table in PowerShell.

Think of a hash table as a labeled box where you put and get items by their labels.

What happens when you try to get a value from a hash table using a key that does not exist? How can this behavior be useful?

Consider how you might safely check for data without breaking your script.