Python基础拾遗

1. list使用sort排序

Python2中的list既可以是字符串和数字，然后使用sort排序，排序的时候使用Ascall码。

list1 = [‘a‘,‘b‘,123]
list1.sort()
print list1
# 运行结果：[123, ‘a‘, ‘b‘]

Python3中的list必须是纯数字才可以排序。

list1 = [‘a‘,‘b‘,123]
list1.sort()
# 运行结果：
Traceback (most recent call last):
File "C:/Users/Administrator/PycharmProjects/20180119/index.py", line 12, in <module>
list1.sort()
TypeError: ‘<‘ not supported between instances of ‘int‘ and ‘str‘

2.  应熟练使用dict.setdefault()函数

result = {}
data = [{'domain': "baidu.com", "kw": "张三"},{'domain': "baidu.com", "kw": "李四"}, {'domain': "baidu2.com", "kw": "王五"}, {'domain': "jd.com", "kw": "田陆"}]
for it in data:
    result.setdefault(it.get("domain"), []).append(it.get("kw"))
print data
# 运行结果
[{'domain': 'baidu.com', 'kw': 'xe5xbcxa0xe4xb8x89'}, {'domain': 'baidu.com', 'kw': 'xe6x9dx8exe5x9bx9b'}, {'domain': 'baidu2.com', 'kw': 'xe7x8ex8bxe4xbax94'}, {'domain': 'jd.com', 'kw': 'xe7x94xb0xe9x99x86'}]