print commas after each print statement except the last one - foreach

Question

I need some help with my foreach loop logic:
I need to put a comma after each print statement except for the last statement in the loop
ex: blah,blah2,blahlast
The following code puts comma even after the last statement.
foreach row $regions {
set name [lindex $row 0]
set id [lindex $row 1]
puts "{'name':'$name', 'val':'$region_id'}"
puts ","
}
Maybe if i count the number of times its going to loop, I can probably check for an if condition to put comma unlti its the last iteration

Answer 1

Another way to approach it is to build a list of items to print and join it at the end:
set lines {}
foreach row $regions {
set name [lindex $row 0]
set region_id [lindex $row 1] ;# changed this from id to region_id, seemed right
lappend lines "{'name':'$name', 'val':'$region_id'}"
}
puts [join $lines ",\n"]

Answer 2

The trick is to print the comma on all the iterations but the first one (that is, to reverse your logic):
set xs {a b c}
set s ""
set need_comma false
foreach x $xs {
if {$need_comma} {
append s ,
} else {
set need_comma true
}
append s $x
}
puts $s
would produce
a,b,c
Note that it seems you're merely looking for the join command.

Answer 3

I voted +1 for RHSeeger because that is what I would do. However, it seems you are trying to convert a TCL list to Python's list. If that is the case, you don't even have to worry about suppressing the last comma: Python allows that:
>>> li = [1,2,3,]
>>> len(li)
3
That means, your current solution works. Don't worry about the last comma.