Question

我有这段代码当前针对一个列表运行for循环

data3 = []
x=0 
while x<len(river_df_list):
    for line in river_df_list[x]: 
        try: 
            distance = haversine(river_df_list[x][0],river_df_list[x][1],df1_list[0][4],df1_list[0][3])
            data3.append(distance)
            x=x+1
        except IndexError:
            pass

df1_list[0].append(data3.index(min(data3)))

haversine函数的位置：

def haversine(lon1, lat1, lon2, lat2):
    """
    Calculate the great circle distance between two points 
    on the earth (specified in decimal degrees)
    """
    # convert decimal degrees to radians 
    lon1, lat1, lon2, lat2 = map(radians, [lon1, lat1, lon2, lat2])

# haversine formula 
dlon = lon2 - lon1 
dlat = lat2 - lat1 
a = sin(dlat/2)**2 + cos(lat1) * cos(lat2) * sin(dlon/2)**2
c = 2 * asin(sqrt(a)) 
r = 6371 # Radius of earth in kilometers. Use 3956 for miles
return c * r

river_df_list（缩短）如下：

[[151.7753278, -32.90526725, 'HUNTER RIVER']
[151.77526830000002, -32.90610052, 'HUNTER RIVER']
[151.775397, -32.90977754, 'HUNTER RIVER']
[151.775578, -32.91202941, 'HUNTER RIVER']
[151.77586340000002, -32.91508789, 'HUNTER RIVER']
[151.7764116, -32.91645856, 'HUNTER RIVER']
[151.7773432, -32.91905274, 'HUNTER RIVER']
[151.7784225, -32.91996844, 'HUNTER RIVER']
[151.780565, -32.92181352, 'HUNTER RIVER']
[151.7807739, -32.92183623, 'HUNTER RIVER']
[151.78591709999998, -32.92187872, 'HUNTER RIVER']]

df1_list（缩短）如下：

[[5, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '14/08/2015']
[6, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '15/08/2015']
[7, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '16/08/2015']
[8, 'A69-1601-27466', 'Golden perch', -35.5065473, 144.4488804, '17/08/2015']]

当前，当我在顶部运行代码时，我可以遍历river_df_list并在df1_list中的第一点应用Haversine函数。最后，代码将在data3中出现最小值的位置的索引附加到df1_list，因此现在看起来像：

[5, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '14/08/2015',324110 ]
[6, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '15/08/2015']
[7, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '16/08/2015']
[8, 'A69-1601-27466', 'Golden perch', -35.5065473, 144.4488804, '17/08/2015']

我想要做的是更改顶部的while / for循环，以比较df1_list的每个点上river_df_list的所有点，并将索引附加到df1_list的末尾，这样最终就可以了输出为：

[[5, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '14/08/2015',324110 ]
[6, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '15/08/2015',32440]
[7, 'A69-1601-27466', 'Golden perch', -35.495479100000004, 144.45295380000002, '16/08/2015',31110]
[8, 'A69-1601-27466', 'Golden perch', -35.5065473, 144.4488804, '17/08/2015',35479]]

我该怎么做？

Answer 1

这应该有效：

for x in df1_list:
    data3 = []
    for y in river_df_list:
        distance = haversine(y[0],y[1],x[4],x[3])
        data3.append(distance)
    x.append(data3.index(min(data3)))

因为您需要每个点都与其他点关联，所以使用嵌套循环并同时完成这两个过程。对于df1中的每个数组，您要遍历river_df的所有内容，获取hasrsines并将其保存到data3中。然后，您将从data3中获取最小值并将其附加到该数组上，然后再移至df1中的下一个数组。它正在处理您提供的玩具数据。

编辑：而且，data3似乎非常昂贵（在时间和内存上），并且不必要，因为您只真正想要最小值的索引。这样可以消除它：

from sys import maxsize

for x in df1_list:
    min_distance = [maxsize, 0]
    for i, y in enumerate(river_df_list):
        distance = haversine(y[0],y[1],x[4],x[3])
        if distance < min_distance[0]:
            min_distance = [distance, i]
    x.append(min_distance[1])

我正在使用maxsize，因为我不知道这些距离有多大。如果它们永远不会大于1000000，则可以改用它。

清单上的While和for循环

1 个答案: