python_瑣碎

python 瑣碎

瑣碎點

string.format

自python2.6開始，新增了一種格式化字符串的函數str.format()

它通過{}和:來代替%。

* 通過位置 *

In [1]: '{0},{1}'.format('kzc',18)  
Out[1]: 'kzc,18'  
In [2]: '{},{}'.format('kzc',18)  
Out[2]: 'kzc,18'  
In [3]: '{1},{0},{1}'.format('kzc',18)  
Out[3]: '18,kzc,18'

* 通過關鍵字參數 *

In [5]: '{name},{age}'.format(age=18,name='kzc')  
Out[5]: 'kzc,18'

* 通過對象屬性 *

class Person:  
    def __init__(self,name,age):  
        self.name,self.age = name,age  
        def __str__(self):  
            return 'This guy is {self.name},is {self.age} old'.format(self=self)  

In [2]: str(Person('kzc',18))  
Out[2]: 'This guy is kzc,is 18 old'

* 通過下標 *

In [7]: p=['kzc',18]
In [8]: '{0[0]},{0[1]}'.format(p)
Out[8]: 'kzc,18'

yield 迭代器

修飾符@

list/dict遍歷

list遍歷

a = ["a", "b", "c", "d"]

直接取值
for i in a:
    print i

取索引
for i in xrange(len(a)):
    print i, a[i]

enumerate取索引取值 
for i, el in enumerate(a):
    print i, el

從1開始遍歷
for i, el in enumerate(a, 1):
    print i, el

dict遍歷

d = {'a': 1, 'c': 3, 'b': 2, 'd': 4}

for k in d:
    print k, d[k]


for k, v in d.iteritems():
    print k, v