Modifying Element In For List
steve-REMOVE-THIS at cybersource.com.au
Tue Nov 16 06:17:37 CET 2010
On Mon, 15 Nov 2010 08:31:52 -0800, octopusgrabbus wrote:
> My question concerns elementary list and pass by reference:
What does pass-by-reference have to do with Python? Python doesn't use
pass-by-reference... if you think it does, you have misunderstood
Hint: if you think Python has pass-by-reference, please write a procedure
that takes two generic arguments, and swaps their values, like so:
a = 1
b = 2
assert a == 2
assert b == 1
This is the canonical test for pass by reference semantics.
> I've written a function which is passed a list that contains rows read
> from a csv file.
What are the rows? Lists? Tuples? Something else?
> The function traverses csv_rows, row by row, and
> inspects the first element in each row. The function tests for '', and
> if true, replaces that with a 0.
> I've used the standard Python for syntax for this.
As opposed to C++ syntax or Lisp syntax?
You can't write Python code without using Python syntax, so I'm not sure
what you mean here.
> def cleanMeterID(csv_rows, bad_meter_id_count):
> d = drIdx()
> row_number = 0
> for row in csv_rows:
> if False == is_number(row[d.MeterID]):
> csv_rows[row_number][d.MeterID] = 0
> row_number = row_number + 1
> bad_meter_id_count= bad_meter_id_count + 1
> print("Received ", bad_meter_id_count, " bad meter ids")
> I believe the logic show above is flawed, because I am not modifying
> elements in the original csv_rows list.
Are you sure about that? What happens when you try it?
> I would modify this to use an
> index to traverse the list like
This is nearly always the wrong solution in Python.
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