将 none 值替换为同一列表中的值

Question

我是python的新手，我正在为这个例子而苦苦挣扎。我想用列表中的日期替换空元素。例如，每个空元素都被星期一替换到星期二...我使用的是蟒蛇2.7。这是我得到的列表：[u'Monday 30 March', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'Tuesday 31 March', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'Wednesday  1 April', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'', u'']这就是我尝试过的：for tim in time_d:    if tim =='':        print time_d[0]

Answer 1

你在寻找吗？如下所示：

for i, val in enumerate(time_d):

    if not val:

        time_d[i] = time_d[i-1]

time_d

# ['Monday 30 March', 'Monday 30 March', ... ,'Monday 30 March', 

#  'Tuesday 31 March', 'Tuesday 31 March', ... , 'Tuesday 31 March', 

#  'Wednesday  1 April', 'Wednesday  1 April', ..., 'Wednesday  1 April']

Answer 2

这是一个简单的解决方案（在Python 3中）：

dates = ['Monday 30 March', '', '', '', '', '', '', '', '', '', 'Tuesday 31 March', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', 'Wednesday  1 April', '', '', '', '', '', '', '', '', '', '', '', '', '', '']     

newdates = []

current = ''

for item in dates:

    if not item:

        newdates.append(current)

    else:

        current = item

        newdates.append(current)

print(dates)

print(newdates)

带输出：

['Monday 30 March', '', '', '', '', '', '', '', '', '', 'Tuesday 31 March', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', 'Wednesday  1 April', '', '', '', '', '', '', '', '', '', '', '', '', '', '']

['Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Monday 30 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Tuesday 31 March', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April', 'Wednesday  1 April']