python求众数问题实例

list_num = []
list_num_count = 0
dict_num ={}
#从文件读入,文件第一行为集合中元素的个数,以后每一行为一个元素
list_num_count = int(open('input.txt','r').readline())
for line_num, line in enumerate(open("input.txt",'r')):
  if line_num > 0:
    list_num += line.split()
#将读到的元素加入的字典中
for item in list_num:
  if dict_num.has_key(item):
    dict_num[item] += 1
  else:
    dict_num.setdefault(item,1)
  pass

#找到出现次数最多的那个数,找到重数
dict_sort_by_top = {}
top_value = 0
for valus in dict_num.itervalues():
  if valus> top_value:
    top_value = valus
  pass

#根据重数找到众数...这是因为考虑到可能有多个元素有相同多的重数
the_pop_num = 0
the_pop_num_count = 0
for keys,values in dict_num.iteritems():
  if values == top_value:
    print 'the pop num is %s,and the appear num is %s' % (keys,values)
    the_pop_num = keys
    the_pop_num_count = values
#输出到文件,第一行为从数,第二行为重数
write_line = '%s\n%s' %(the_pop_num, the_pop_num_count)
open("output.txt",'w').write(write_line)

8
11
37
2
37
2
45
99
37

the pop num is 37,and the appear num is 3