对象与引用

对象与引用
例9.6 对象与引用
#!/usr/bin/python
# Filename: reference.py

print 'Simple Assignment'
shoplist = ['apple', 'mango', 'carrot', 'banana']
mylist = shoplist # mylist is just another name pointing to the same object!

del shoplist[0]

print 'shoplist is', shoplist
print 'mylist is', mylist
# notice that both shoplist and mylist both print the same list without
# the 'apple' confirming that they point to the same object

print 'Copy by making a full slice'
mylist = shoplist[:] # make a copy by doing a full slice拷贝一个列表 用切片操作符
del mylist[0] # remove first item

print 'shoplist is', shoplist
print 'mylist is', mylist
# notice that now the two lists are different

你需要记住的只是如果你想要复制一个列表或者类似的序列或者其他复杂的对象（不是如整数那样的简单 对象 ），那么你必须使用切片操作符来取得拷贝。如果你只是想要使用另一个变量名，两个名称都 引用 同一个对象，那么如果你不小心的话，可能会引来各种麻烦。