Python dictionary 复制实现方法

Python dictionary 复制实现方法

L = [1,2,3]
D = {'a':1, 'b':2}

A = L[:] # instead of: A = L (or list(L))
B = D.copy() # instead of: B = D

A[1] = 'Ni'
B['c'] = 'spam'

print L, D

print A, B

#The copy method returns a new dictionary with the same key-value pairs (a "shallow
#copy," since the values themselves are the same, not copies):

x = {'username': 'admin', 'machines': ['foo', 'bar', 'baz']}
y = x.copy()
y['username'] = 'mlh'
y['machines'].remove('bar')
print y

print x

from copy import deepcopy
d = {}
d['names'] = ['Alfred', 'Bertrand']
c = d.copy()
dc = deepcopy(d)
d['names'].append('Clive')
print c
print dc