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Tag: scala (Page 2 of 2)

Random numbers with PowerShell

March 21, 2021 /

Recently, I was writing some unit tests for a data transformation application I had been developing. I had a sample file of pre-transformed data and decided I wanted my unit tests to just test a few, randomly selected records from the file. My tests would pull in the data file as a list and would iterate through a list of randomly determined indices and test the transformation of each data row. Something like this:

val randomRows = Seq(1, 2, 3, 4, 5) 
for (i <-0 to randomRows.length-1) {
  val randomRow = randomRows(i)
  val dataToTest = dataList(randomRow)
  // transform the data; assert the results
}

But, instead of “1, 2, 3, 4, 5”, I wanted random indices like “432, 260, 397, 175, 98.” How could I quickly achieve this and get different sets of random numbers for the different unit tests I was writing?

Random.org is certainly a good option for picking random numbers. Suppose I had 10 unit tests to write, each needing to test 5 random rows of data. I could generate 50 random numbers like so:

108	62	221	275	342
303	475	234	283	343
184	42	454	102	423
48	348	289	37	493
258	471	461	212	278
175	56	224	405	354
374	124	328	17	171
416	266	415	436	414
93	155	140	382	235
83	382	449	302	170

That’s great, but, annoyingly, I still have to edit these numbers and type commas in between each when I paste them into my code. Is there a way to generate the random numbers I need and automatically format them with commas so that I can easily paste them into my unit test code? PowerShell can do that!

The Get-Random cmdlet

PowerShell has a fantastic cmdlet called Get-Random that allows you easy access to Microsoft’s random number generator features. To use Get-Random to randomly select 5 indices to use in one of my unit tests, I can execute this command at a PowerShell prompt:

0..500 | Get-Random -Count 5

Here, I’m piping a list of numbers–from 0 to 500–to Get-Random and telling the cmdlet to randomly select 5 of them. The result is this:

283
331
212
397
459

The problem is that I’m still no better off that with Random.org: I still must manually comma-delimit these numbers so that they can fit into my code.

Formatting my random numbers

Fortunately, PowerShell includes a handy join operator to make joining my list of random numbers a breeze. All I need to do is surround my original PowerShell command with parentheses and apply a join operation to that result set:

(0..500 | Get-Random -Count 5) -join ", "

And the result:

121, 123, 231, 45, 70

Easy-peasy! I can now drag my mouse over that result, right-click on it to copy the formatted numbers to my clipboard, and then paste the results into my unit test.

But wait, there’s more

That mouse highlighting and right-clicking still seems like a bit of work. Is there anything else I can do to shorten my steps further? Absolutely! PowerShell has another great cmdlet called Set-Clipboard allowing you push PowerShell results right into your clipboard. So, I can just pipe my formatted, random numbers right into the Windows clipboard:

(0..500 | Get-Random -Count 5) -join ", " | Set-Clipboard

Now, once I run the PowerShell command, I can just hop right into my code editor, position my cursor at the appropriate position, and paste in my random numbers. Quite a convenient little command!

Iterating over a date range

August 13, 2020 /

I leverage a number of different programming and scripting tools. Recently, I found myself in a situation where I had to write code to loop through a range of dates to do some operations, by month, in not one, not two…but three different languages: Scala, Python, and Bash. The coding principles are the same across the technologies, but the syntax sure is different.

Here are code examples in four technologies–I threw in PowerShell for good measure–for looping through a range of dates. I loop by month, but these could easily be adapted to loop by day or year or whatever increment fits your needs.

Scala

import java.time.LocalDate
import java.time.format.DateTimeFormatter
import java.util.Date

val start = LocalDate.of(2020, 1, 1) // inclusive in loop
val end = LocalDate.of(2020, 9, 1) // excluded from loop

val template = "This loop is for Year %1$d and Month (zero padded) %2$s \n"

val date_range = Iterator.iterate(start) { _.plusMonths(1) }.takeWhile(_.isBefore(end))
while(date_range.hasNext){
	val d = date_range.next
	val s = template.format(d.getYear, d.format(DateTimeFormatter.ofPattern("MM")))
	print(s)
}

Python

import datetime
import calendar

start = datetime.date(2020, 1, 1)
end = datetime.date(2020, 9, 1)
template = "This loop is for Year {0} and Month (zero padded) {1:%m}"

while start != end:
	s = template.format(start.year, start)
	print(s)
	days_in_month = calendar.monthrange(start.year, start.month)[1]
	start = start + datetime.timedelta(days=days_in_month)

Bash

start=2020-1-1
end=2020-9-1

while [ "$start" != "$end" ]; do
	s="`date -d "$start" +"This loop is for Year %Y and Month (zero padded) %m"`"
	echo s
	start=$(date -I -d "$start + 1 month")
done

PowerShell

$start = get-date "2020-1-1"
$end = Get-Date "2020-9-1"

while($start -ne $end){
    "This loop is for Year {0:yyyy} and Month (zero padded) {0:MM}" -f $start
    $start = $start.AddMonths(1)
}
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