欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页

[转载]Python中列表append()、extend()、"+"、"+="的区别

程序员文章站 2024-01-06 13:45:54
...

原文地址:Python中列表append()、extend()、"+"、"+="的区别
第一:添加一个元素到列表中

# encoding=utf-8
a = ["a", "b", "c"]
print "append|添加前id:%s" % id(a),
a.append("d")
print "添加后id:%s" % id(a), a
print "-"*62
 
a = ["a", "b", "c"]
print "extend|添加前id:%s" % id(a),
a.extend("d")
print "添加后id:%s" % id(a), a
print "-"*62
 
a = ["a", "b", "c"]
print "     +|添加前id:%s" % id(a),
a = a + ["d"]
print "添加后id:%s" % id(a), a
print "-"*62
 
a = ["a", "b", "c"]
print "    +=|添加前id:%s" % id(a),
a += "d"
print "添加后id:%s" % id(a), a

输出结果:


append|添加前id:40672072 添加后id:40672072 ['a', 'b', 'c', 'd']
--------------------------------------------------------------
extend|添加前id:40683080 添加后id:40683080 ['a', 'b', 'c', 'd']
--------------------------------------------------------------
       +|添加前id:40672072 添加后id:40683208 ['a', 'b', 'c', 'd']
--------------------------------------------------------------
     +=|添加前id:40672072 添加后id:40672072 ['a', 'b', 'c', 'd']

可以看出这四种方式都可以向列表中添加一个新元素,除了"+"之外,其他三种方式都是在原列表上添加数据,"+"则会创建一个新的列表,并且"+"只能连接两个列表,如果连接一个元素跟一个列表会报错

第二:添加一个列表到列表中

# encoding=utf-8
a = ["a", "b", "c"]
print "append|添加前id:%s" % id(a),
a.append(["d","e","f"])
print "添加后id:%s" % id(a), a
print "-"*62
 
a = ["a", "b", "c"]
print "extend|添加前id:%s" % id(a),
a.extend(["d","e","f"])
print "添加后id:%s" % id(a), a
print "-"*62
 
a = ["a", "b", "c"]
print "     +|添加前id:%s" % id(a),
a = a + ["d","e","f"]
print "添加后id:%s" % id(a), a
print "-"*62
 
a = ["a", "b", "c"]
print "    +=|添加前id:%s" % id(a),
a += ["d","e","f"]
print "添加后id:%s" % id(a), a

输出结果:


append|添加前id:40082248 添加后id:40082248 ['a', 'b', 'c', ['d', 'e', 'f']]
--------------------------------------------------------------
extend|添加前id:40093384 添加后id:40093384 ['a', 'b', 'c', 'd', 'e', 'f']
--------------------------------------------------------------
       +|添加前id:40082248 添加后id:40082376 ['a', 'b', 'c', 'd', 'e', 'f']
--------------------------------------------------------------
     +=|添加前id:40082248 添加后id:40082248 ['a', 'b', 'c', 'd', 'e', 'f']

append方法当添加的元素是列表时会回将整个列表添加进原列表,extend与"+="的效果是一样的,会将列表中的元素添加到原列表,"+"也会将两个列表中的元素复制到一个新创建的列表中,所不同的会创建一个新的列表

转载于:https://www.jianshu.com/p/73e7a35326a7

上一篇:

下一篇: