```
from copy import deepcopy
""" Singly linked list example,
in real life better to use blist module
easy_install blist
"""
class Node(object):
__slots__ = 'data', 'next_node'
def __init__(self, value, next_node=None):
self.data = value
self.next_node = next_node
def __str__(self):
return 'Node(%r)' % self.data
__repr__ = __str__
class List(object):
def __init__(self, *info):
self.head = None
if info:
current = self.head = Node(info[0])
for n in info[1:]:
current.next_node = Node(n)
current = current.next_node
def __iter__(self):
current = self.head
if current is not None:
yield current
else:
return
while current.next_node != None:
current = current.next_node
yield current
def __str__(self):
return 'List(%s)' % ', '.join(repr(node.data) for node in self)
__repr__ = __str__
def __len__(self):
if not self.head:
return 0
return sum(1 for i in self)
def __add__(self, other):
copy = deepcopy(self)
copy.append(other)
return copy
def __radd__(self, other):
copy = deepcopy(self)
copy.append(other)
return copy
def append(self, other):
end = None
for end in self:
pass
if end is None:
self.head = other.head
else:
end.next_node = other.head
def insert(self, node, pos=0):
prev = node
for count, element in enumerate(self):
if count == pos:
node.next_node = element
if not pos:
self.head = node
else:
prev.next_node = node
return
prev = element
self.append(List(*(None for c in range(pos - count - 1))))
self.append(List(node.data))
def delete(self, value):
node_before = Node(None)
for node in self:
if node.data == value:
if node_before.next_node:
node_before.next_node = node.next_node
else:
self.head = node.next_node
return
else:
node_before = node
raise ValueError('Node value %s not in List' % value)
def __getitem__(self, n):
for count, node in enumerate(self):
if count == n:
return node.data
raise IndexValue('List index out of range')
def __setitem__(self, n, value):
for count, node in enumerate(self):
if count == n:
node.data = value
return
raise IndexValue('List index out of range')
def find(self, value):
for node in self:
if node.data == value:
return node
raise ValueError('Value %r not in List' % value)
if __name__ == '__main__':
test_list = List('a', 'b', 'c')
print test_list
for node in test_list:
print node.data
other_list = List('d')
print other_list, 'Length', len(other_list)
test_list.append(other_list)
print 'Appended', test_list, 'Length', len(test_list)
test_list.delete('d')
print "Deleted node with value 'd'", test_list, 'Length', len(test_list)
try:
test_list.find('z')
print('Value %s found' % 'z')
except ValueError as e:
print(e)
for value in test_list:
test_list.delete(value.data)
print value, 'deleted: ', test_list, 'Length', len(test_list)
test_list.append(List(*'abcdefg'))
print test_list
test_list.append(List(*range(10)))
print test_list
test_list.insert(Node('z'), 23)
print test_list
print len(test_list)
print test_list[4]
test_list[4] = 4
print test_list
print test_list+ List('more test')
print 'Test list did not change:', test_list
```

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