list 2 dict?

Tue Jan 4 13:07:48 EST 2011

Here is something totally the opposite of a nice one liner:
A hackish module with a bloated generator. Feel free to comment, so I
can learn the errors of my ways. Try not to be too mean though. Try to
think of the attached file as a demonstration of ideas instead of good
coding practices.
Don't be afraid to mention the good points too.
I tried to send an email with an attachment (to hide my shame) but I
kept getting email rejections.
# =======================================================
# list2dict.py
# list item to dict item generator
# I forget if generators are thread safe
# DevPlayer at gmail.com
# 2011-01 Jan-03
#
def check_slice_bounds(list_len, start, stop, step):
 """Incomplete slice checker."""
 # -----------------------------
 # force step to be non-None
 if step is None:
 step = 1
 # -----------------------------
 # force step to be non-zero
 if step == 0:
 step = 1
 # -----------------------------
 # in iterating over list to be converted to dict
 # where list == [key, value, key, value] or in case swap==True
 # list = [value, key, value, key]
 # actual stepping is one for key, and plus one more for value
 step = step * 2
 # -----------------------------
 # force step to be smaller then size of list or -size of list
 if step > 0:
 if step > list_len:
 step = list_len
 else:
 if step < -list_len:
 step = -list_len
 # -----------------------------
 # force step to be even for key, value iteration
 if step % 2 == 1:
 if step > 0:
 step = step - 1
 else:
 step = step + 1
 # -----------------------------
 # set start to default; depending on step direction (+x vs -x)
 if start is None:
 if step > 0:
 start = 0
 elif step == 0:
 start = 0
 stop = start
 else:
 start = -1
 # -----------------------------
 # set stop to default; depending on step direction (+x vs -x)
 if stop is None:
 if step > 0:
 stop = list_len-1
 elif step == 0:
 stop = start
 else:
 stop = -list_len
 # -----------------------------
 # convert "start" to equivelent positive index
 if start < 0:
 if start < -list_len:
 raise IndexError("IndexError: list index out of range:",
start)
 else:
 start = list_len + 1 + start
 # -----------------------------
 # convert "stop" to equivelent positive index
 if stop < 0:
 if stop < -list_len:
 raise IndexError("IndexError: list index out of range:",
stop)
 else:
 stop = list_len + 1 + stop
 return (start, stop, step)
def gen(lyst, dyct=None, start=None, stop=None, step=None,
swap=False):
 """
 lyst == list to convert to dict
 dyct == external dict to be updated
 start == starting index
 stop
 step == amount to move index by; usually +1 or -1 (times 2)
 could be a float if clever enough.
 if step equals zero it is converted to 1 to prevent
 an infinite loop.
 step will be reset to be an index inbounds of a list len()
 swap 2nd item with the first item in the yield
 """
 # -----------------------------
 # Force into bool True or False from equivelent values
 if swap == True: swap = True
 else: swap = False
 # -----------------------------
 # check and set lyst slice/index bounds of start, stop, step
 start, stop, step = check_slice_bounds(len(lyst), start, stop,
step)
 # -----------------------------
 index = start
 # -----------------------------
 while 0 <= index < len(lyst):
 next = index + 1
 if next == len(lyst):
 value = None
 else:
 value = lyst[next]
 key = lyst[index]
 # -----------------------------
 # update external dict if given
 if dyct is not None:
 dyct[key] = value
 # -----------------------------
 # effectively sway key with value == index, index+1 to index
+1, index
 if swap:
 newindex = yield (value,key)
 else:
 newindex = yield (key,value)
 # -----------------------------
 # process "newindex" variable if caller does a
 # gen.send(some_list_index) externally
 if newindex is None:
 index = index + (step)
 elif 0 <= newindex < len(lyst):
 # fix this to allow for negative index for negative
stepping
 # but don't forget to convert it to its corrosponding
 # positive index
 index = newindex
 else:
 # fix this so it doesn't error on index 0
 #raise IndexError("Index is out of range:", index)
 pass
 # -----------------------------
 # Ungracefully coerce end of iteration
 if step > 0:
 if index > stop:
 # fix to raise StopIteration
 break
 else:
 if index < stop:
 # fix to raise StopIteration
 break
# Example usage
testlist = [1, 2, 3, 4, 5, 6, 7, 'a', 8, 'b']
# --------------------
d = {}
e = {y[0]:y[1] for y in gen(testlist,d)}
print d
print d
print 'next demo1'
# --------------------
d = {}
e = {y[1]:y[0] for y in gen(testlist,d)}
f = {y[0]:y[1] for y in gen(testlist,d, swap=True)}
print d
print e
print f
print 'next demo2'
# --------------------
d = {}
for x in gen(testlist,d):
 print x
print d
print 'next demo3'
# --------------------
d = {}
e = [y for y in gen(testlist,d,swap=True)]
print d
print e
print 'next demo4'
# --------------------
d = {}
e = gen(testlist,d)
try:
 while e.next(): pass
except:
 pass
print d
#print 'next demo'