python--随笔一

1.format函数--根据关键字和位置选择性插入数据

In [11]: '{mingzi}jintian{dongzuo}'.format(mingzi='duzi',dongzuo='i love you')
Out[11]: 'duzijintiani love you'

In [12]: '{1}jintian{0}'.format('duzi','i love you')
Out[12]: 'i love youjintianduzi'

In [13]: '{0}jintian{1}'.format('duzi','i love you')
Out[13]: 'duzijintiani love you'

In [14]: '{0}jintian{0}'.format('duzi','i love you')
Out[14]: 'duzijintianduzi

2.不使用Python内置函数对列表进行排序

#-*- coding:utf-8 -*-

a = [1,4,5,6,2,8,4]
alen = len(a)
for x in xrange(1,alen):
    if a[x-1] > a[x]:
        a[x],a[x-1] = a[x-1],a[x]
        for j in xrange(1,alen):
            if a[j-1] > a[j]:
                a[j],a[j-1] = a[j-1],a[j]
print a

 3.python之json

json.dumps  将 Python 对象编码成 JSON 字符串
json.loads  将已编码的 JSON 字符串解码为 Python 对象

代码实例:

#语法
#json.dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, encoding="utf-8", default=None, sort_keys=False, **kw)
#ensure_encoding='utf-8' 防止中文乱码
#indent=4 缩进为4
#separators=(',',':') items之间用','分开,key:value使用'：'分开

import json
data = [{'a':1,'b':2,'c':3,'d':4,'e':5}]
json_str = json.dumps(data,ensure_ascii='utf-8',sort_keys=True,indent=4,separators=(',',':'))
with open('data.json', 'w') as f:
    f.write(json_str)
'''
[
    {
        "a":1,
        "b":2,
        "c":3,
        "d":4,
        "e":5
    }
]
'''

#json.loads(s, encoding=None, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw

print json.loads(json_str)

#[{u'a': 1, u'c': 3, u'b': 2, u'e': 5, u'd': 4}]

 traceback:捕获并打印异常

import traceback

try:
    1/0
except Exception, e:
    #traceback.print_exc()
    #c = traceback.format_exc()
    #print(c)
    traceback.print_exc(file=open('nihao.txt','w+'))

'''
    traceback.print_exc()跟traceback.format_exc()有什么区别呢？
    format_exc()返回字符串，print_exc()则直接给打印出来。
    即traceback.print_exc()与print traceback.format_exc()效果是一样的。
    print_exc()还可以接受file参数直接写入到一个文件。比如
    traceback.print_exc(file=open('tb.txt','w+'))
    写入到tb.txt文件去。
'''

 快速排序

def quicklist(list1):
    if len(list1) < 1:
        return list1

    less = []
    base = list1.pop()
    max  = []

    for i in list1:
        if i  < base:
            less.append(i)
        else:
            max.append(i)

    return quicklist(less) + [base] + quicklist(max)

if __name__== '__main__':
    lis= [1,2,6,3,4,5,9,6]
    a = quicklist(lis)
    print (a)

sort,sorted

a = [1,2,4,3,5,9,5]
a.sort(reverse=True)
b = a.sort(reverse=True)
c =sorted(a)
print b
print a
print c

None
[9, 5, 5, 4, 3, 2, 1]
[1, 2, 3, 4, 5, 5, 9]