Replace element in list with element from another list - Python -

Replace element in list with element from another list - Python -

i have list named rule.start. in list, elements equal element list called com.empty. want element rule.start replaced element comes after same element com.empty. how this?

rule.start looks this:

['f', 'l', 'g', 'l', 'f', 'r', 'f', 'r', 'f', 'l', 'g', 'l', 'f', 'l', 'f', 'l', 'g', 'l', 'f', 'l',........]

com.empty looks this:

['f', ['fd'], 'g', ['fd'], 'l', ['lt', '60'], 'r', ['rt', '60']]

i have tried this:

wut = 0 elem in rule.start: v = 1 mel in com.empty[::2]: if elem == mel: rule.start[wut] = com.empty[v] print elem print mel wut +=1 v += 2

but replaces element of rule.start ['fd']

in end, want evaluate elements commands, looks this: fd(var, scale)

and this: rt(var, 60) # 60 list.

first, much easier write, , lot more efficient, if had dictionary, mapping keys values, instead of list of alternating keys , values. can one-liner:

mapping = dict(zip(com.empty[::2], com.empty[1::2]))

but if don't understand how works, can this, should able understand (based on code).

mapping = {} key = none mel in com.empty: if key none: key = mel else: mapping[key] = mel key = none

or, better, if possible, alter code build dict instead of list of alternating values in first place.

now, 1 time have this, loop becomes dead simple, , hard wrong:

for wut, elem in enumerate(rule.start): rule.start[wut] = mapping.get(elem, elem)

i'm using enumerate don't have maintain track of wut manually, , i'm using dict.get method instead of looping on keys , values, tricky part got lost in.

or, more simply:

rule.start = [mapping.get(elem, elem) elem in rule.start]

but, if want know what's wrong attempt:

you start off v = 1. each mel, increment v 2 if elem == mel. otherwise, stays @ 1. so, first time elem == mel, you're going have v = 1, you're going assign com.empty[1] rule.start[wut]. if move v + 2 outside loop, prepare problem.

you have similar problem wut += 1 beingness in wrong place. should updated every elem; instead, it's updated every elem , mel match, 0 times or (theoretically) 3 times.

getting stuff right big source of errors, why enumerate exists.

python list