Find and replace inside one csv column with powershell - powershell

Question

I have a large CSV file that looks like this named student.export.text
Student Number,Last Name,Middle Name,First Name,Schoolid,Grade Level,Dob
I'm trying to build an automated task that will run nightly so that another piece of software can understand the CSV correctly.
Here is my code, but I'm missing something that is causing an error. I am new to Powershell and I am hoping for some advice.
Any help will be greatly appreciated!
$Replacements = #{
"5" = "AE";
"7" = "ER";
"10" = "FM";
"12" = "HC";
"14" = "JH";
"18" = "LE";
#...]
}
Import-Csv .\student.export.text | ForEach-Object {
$_.Schoolid = $Replacements[$_.Schoolid]
$_
} | Export-Csv -NoTypeInformation .\new.csv

Answer 1

Here's one approach that can work.
# declare hash table with School ID to School Name mapping
$schoolIdsToNames = #{
"3" = "SchoolA";
"4" = "SchoolB"
}
# import the CSV file
$csv = Import-Csv "C:\input.csv";
# for each row, replace the School ID field with the School Name
foreach($row in $csv)
{
$row.Schoolid = $schoolIdsToNames[$row.Schoolid];
}
# export the modified CSV
$csv | Export-Csv "C:\replaced.csv" -NoTypeInformation;
In the first step, we set up a PowerShell hashtable (a sort of key-value pair list), then import the CSV file using Import-Csv and store it in the $csv variable. This cmdlet will create an object from every row of the CSV that we can manipulate easily. For each row, we simply replace the Schoolid field with the value assigned to the ID key in the $schoolIdsToNames hashtable. Finally, we export the CSV to another file.
Another, more PowerShell-ly approach would be something like this:
Import-Csv "C:\test\school.csv" | Select-Object *, #{ Name = "SchoolName"; Expression = { $schoolIdsToNames[$_.Schoolid] } } | Export-Csv "C:\test\replaced2.csv" -NoTypeInformation
This one-liner imports the CSV and sends it down the pipeline. For each row, we select all properties of the row using Select-Object and add a new property called SchoolName, setting its value using the same hash table-based technique as above. Finally, we export the object list to CSV.