Python：如何在列表中使用附加参数的随机数

Question

My dataset has random dimensions, so that I want to use exec() or eval() to read in my data. Here is my code:

tim = []
var = []
for line in open(fid).readlines():
    str = line.split()
    if line.find('/') >= 0:
       tim.append( datetime.strptime(str[0]+str[1],'%Y/%m/%d%H:%M:%S'))
       depth = int(str[2])
       num = 0
    else:
       if num == 0: 
          for i in range(len(str)): exec('var_%02d = []' %(i))
       for i in range(len(str)): exec('var_%02d.append( str[%d] ) ' % (i,i))
       num += 1
       if num == depth-1:             
          var.append([eval('var_%02d' % i) for i in range(len(str))])

The format of data looks like:

2010/01/01 00:00:00 6 2
  10 20
  15 22
  20 30
  25 28
  35 17
  40 35

Sometimes the data may add another column and looks like:

2010/01/01 00:00:00 6 2
  10 20 18
  15 22 21 
  20 30 30
  25 28 28
  35 17 17
  40 35 32

Generally, my code works fine. But if I want to make if like a function, it is not working. Does anybody know how to append random numbers of parameters together in a list?

Answer 1

You don't need to use exec , actually you should never use exec . Use a multidimensional array (an array of arrays) to collect your numbers:

tmp = []
tim = []
var = []
for line in open(fid).readlines():
    str = line.split()
    if line.find('/') >= 0:
       tim.append( datetime.strptime(str[0]+str[1],'%Y/%m/%d%H:%M:%S'))
       depth = int(str[2])
       num = 0
    else:
       if num == 0:
          for i in range(len(str)):
              if len(tmp) <= i:
                  tmp.append([])
       for i in range(len(str)):
           tmp[i].append(str[i])
       num += 1
       if num == depth-1:
          var.append([tmp[i] for i in range(len(str))])

print(var)

For the first set of data it will print:

[[['10', '15', '20', '25', '35', '40'], ['20', '22', '30', '28', '17', '35']]]

And for the second:

[[['10', '15', '20', '25', '35', '40'], ['20', '22', '30', '28', '17', '35'], ['18', '21', '30', '28', '17', '32']]]