Question

Python newbie here:

I’m writing a market simulation in Python using Pysage, and want to generate an arbitrary number of agents (either buyers or sellers) using the mgr.register_actor() function, as follows:

for name, maxValuation, endowment, id in xrange(5):
    mgr.register_actor(Buyer(name="buyer001", maxValuation=100, endowment=500),"buyer001")
    update name, maxValuation, endowment, id

What is a succinct, pythonic way to run that function call so that, each time the loop is run, the values of name, maxValuation, endowment, and id are changed, e.g. to name="buyer002", name="buyer003"...; maxValuation=95, maxValuation=90...; endowment=450, endowment=400...; "buyer002", "buyer003"... and so on.

I have tried different for-loops and list comprehensions, but haven’t found a way yet to dynamically update the function arguments without running into type issues.

Thanks in advance!

Answer 1

You can prepare the names, maxValuations, and endowments as lists (or iterators), then use zip to group corresponding elements together:

names=['buyer{i:0>3d}'.format(i=i) for i in range(1,6)]
maxValuations=range(100,75,-5)
endowments=range(500,250,-50)
for name, maxValuation, endowment in zip(names,maxValuations,endowments):
    mgr.register_actor(
        Buyer(name=name, maxValuation=maxValuation, endowment=endowment),name)

---

Regarding the format string, '{i:0>3d}':

I refer to this “cheat sheet” when I need to build a format string:

http://docs.python.org/library/string.html#format-string-syntax
replacement_field ::= "{" field_name ["!" conversion] [":" format_spec] "}"
field_name        ::= (identifier|integer)("."attribute_name|"["element_index"]")* 
attribute_name    ::= identifier
element_index     ::= integer
conversion        ::= "r" | "s"
format_spec       ::= [[fill]align][sign][#][0][width][.precision][type]
fill              ::= <a character other than '}'>
align             ::= "<" | ">" | "=" | "^"
                      "=" forces the padding to be placed after the sign (if any)
                          but before the digits. (for numeric types)
sign              ::= "+" | "-" | " "
                      " " places a leading space for positive numbers
width             ::= integer
precision         ::= integer
type              ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" |
                      "o" | "x" | "X" | "%"

So, it breaks down like this:

   field_name 
  /
{i:0>3d}
    \\\\
     \\\`-type ("d" means integer)
      \\`-width 
       \`-alignment (">" means right adjust)
        `-fill character