Python列表添加元素:append和extend比较分析

1 append()

功能:向list添加元素对象,即保持添加元素的完整性;方法无返回值;

• Demo

l_1 = ["tian", "lan", "lan"]
l_2 = ["shui", "qing", "qing"]
l_3 = []
l_3 = l2.append(l_1)
print("append result: {}".format(l_3))
print("append result: {}".format(l_2))

• Result

append result: None
append result: ['shui', 'qing', 'qing', ['tian', 'lan', 'lan']]

• Analysis
  (1) 从l_3返回的返回值为None,可知,append()方法无返回值;
  (2) 从l_2的返回值[‘shui’, ‘qing’, ‘qing’, [‘tian’, ‘lan’, ‘lan’]],第二个元素为一个列表,可知,使用append()方法,向list添加元素对象,保证了添加元素的完整性;

2 extend()

功能:向list添加元素序列,即将元素对象序列话为单独元素,;方法无返回值;

• Demo

l_1 = ["tian", "lan", "lan"]
l_2 = ["shui", "qing", "qing"]
l_3 = []
l_3 = l2.append(l_1)
print("append result: {}".format(l_3))
print("append result: {}".format(l_2))

• Result

append result: None
append result: ['shui', 'qing', 'qing', 'tian', 'lan', 'lan']

• Analysis
  (1) 从l_3返回的返回值为None,可知,append()方法无返回值;
  (2) 从l_2的返回值[‘shui’, ‘qing’, ‘qing’, ‘tian’, ‘lan’, ‘lan’],可知,extend()方法将对象l_1序列化为单个元素,向list添加元素对象,保证了添加序列元素;

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[参考文献]
[1]https://www.cnblogs.com/subic/p/6553187.html

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