(*) Question
How can I, in a single line, write a statement followed by an
expression? For example, if /d/ is a dicionary, how can I write
d["key"] = value # and somehow making this line end up with d
(*) Where does the question come from?
>From the following experiment-exercise.
(*) Introduction
Here's a gentle way to consome records /rs/, each of which represents a
robbery, say, and produce a dictionary containing a count of each zip
code.
--8<---------------cut here---------------start------------->8---
def zip(r):
return r[0]
def roberry_per_zip(rs):
d = {}
for r in rs:
d[zip(r)] = dict.get(d, zip(r), 0) + 1
return d
--8<---------------cut here---------------end--------------->8---
Now I'd like to compare the code with a version that uses reduce. Let
me please write my own reduce function for completeness and clarity ---
I suppose. The code is still pretty clear.
--8<---------------cut here---------------start------------->8---
def my_reduce(it, f, init):
r = init
for e in it:
r = f(r, e)
return r
def count_in(d, r):
d[zip(r)] = dict.get(d, zip(r), 0) + 1
return d
def roberry_via_reduce(rs):
return my_reduce(rs, count_in, {})
--8<---------------cut here---------------end--------------->8---
It's not clear, though, how to write such a procedure using a lambda
expression in place of count_in. That's because we must return a
dicionary and statements are not expressions.
How can I execute a statement followed by a value in a single line?
def roberry_via_reduce(rs):
return my_reduce(rs, lambda d, r: ``increment and return d'', {})
I don't know how to write
``increment and return d''
I'm just curious. Thank you.
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