Hi all
I am new to python but not programming (Although rusty) and am using
Learning Python The Hard Way. I really like it.
System:
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Debian 8 (jessie)
KDE Desktop
Python 2.7 (It's going to be a while before 2,7 goes away. There is just
too much code out there.
Ninja-IDE IDE - I like this a lot. I can't seem to find out how to put
breaks into the code though. The debugger plugin is installed.
--------------
For some reason lesson 39 is hanging and I can't find the cause. A print
statement inserted into the get_slot function just after bucket shows
that get_bucket is returning an []. It' not surprising that enumerate()
doesn't like this very much. I just can't find the cause.
The error message is as follows:
-------------------------------------------
Running: /root/mystuff/mystuff/ex39_test.py (Wed Sep 9
09:57:51 2015)
Traceback (most recent call last):
File "/root/mystuff/mystuff/ex39_test.py", line 6, in <module>
hashmap.set(states, 'Oregon', 'OR')
File "/root/mystuff/mystuff/hashmap.py", line 50, in set
i, k, v = get_slot(aMap, key)
TypeError: 'NoneType' object is not iterable
Execution Successful!
NOTE: Line 50 is the - i, k, v = get_slot(aMap, key)- of def set.
--------------------------------------------
The calling code is:
--------------------------------------------
# -*- coding: utf-8 -*-
import hashmap
# creat a mapping of stat to abbreviation
states = hashmap.new()
hashmap.set(states, 'Oregon', 'OR')
--------------------------------------------
The hashmap code is as follows:
--------------------------------------------
def new(num_buckets=256):
"""Initializes a Map with the given number of buckets."""
aMap = []
for i in range(0, num_buckets):
aMap.append([])
return aMap
def hash_key(aMap, key):
"""Given a key this will create a number and then convert it to
an index for the aMap's buckets."""
return hash(key) % len(aMap)
def get_bucket(aMap, key):
"""Given a key, find the bucket where it would go."""
bucket_id = hash_key(aMap, key)
return aMap[bucket_id]
def get_slot(aMap, key, default=None):
"""
Returns the index, key, and value of a slot found in a bucket.
Returns -1, key, and default (None if not set) when not found.
"""
bucket = get_bucket(aMap, key)
for i, kv in enumerate(bucket):
k, v = kv
if key == k:
return i, k, v
return -1, key, default
def get(aMap, key, default=None):
"""Gets the value in a bucket for the given key, or the default."""
i, k, v = get_slot(aMap, key, default=default)
return v
def set(aMap, key, value):
"""Sets the key to the value, replacing any existing value."""
bucket = get_bucket(aMap, key)
i, k, v = get_slot(aMap, key)
if i >= 0:
# the key exists, replace it
bucket[i] = (key, value)
else:
# the key does not, append to create it
bucket.append((key, value))
def delete(aMap, key):
"""Deletes the given key from the Map."""
bucket = get_bucket(aMap, key)
for i in xrange(len(bucket)):
k, v = bucket[i]
if key == k:
del bucket[i]
break
def list(aMap):
"""Prints out what's in the Map."""
for bucket in aMap:
if bucket:
for k, v in bucket:
print k, v
Very frustrating and probably a stupid error. Any help will be sincerely
appreciated.
Gary R.
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