How to calculate the far and near price programatically?

[The Edge]

Are there any detailed work throughs for calculating the far and near price?

For example, I took some data from one of today's markets. It is attached below. I am not too sure how to reach the far price and near price. A worked example using the data below would be most appreciated!

{'availableToBack': [{'price': 3.0, 'size': 199.7},
{'price': 2.98, 'size': 142.55},
{'price': 2.96, 'size': 48.29},
{'price': 2.94, 'size': 118.08},
{'price': 2.92, 'size': 98.75},
{'price': 2.9, 'size': 283.45},
{'price': 2.88, 'size': 121.39},
{'price': 2.86, 'size': 184.12},
{'price': 2.84, 'size': 177.02},
{'price': 2.82, 'size': 149.17},
{'price': 2.8, 'size': 140.03},
{'price': 2.78, 'size': 105.76},
{'price': 2.76, 'size': 135.14},
{'price': 2.74, 'size': 53.54},
{'price': 2.72, 'size': 41.66},
{'price': 2.7, 'size': 42.15},
{'price': 2.66, 'size': 10.0},
{'price': 2.56, 'size': 12.0},
{'price': 2.54, 'size': 93.07},
{'price': 2.4, 'size': 0.21},
{'price': 2.34, 'size': 107.0},
{'price': 2.32, 'size': 10.0},
{'price': 2.26, 'size': 1.0},
{'price': 2.22, 'size': 252.91},
{'price': 2.02, 'size': 5.0},
{'price': 2.0, 'size': 2504.25},
{'price': 1.83, 'size': 5464.0},
{'price': 1.8, 'size': 1678.35},
{'price': 1.7, 'size': 100.0},
{'price': 1.6, 'size': 5.0},
{'price': 1.51, 'size': 0.35},
{'price': 1.44, 'size': 10.0},
{'price': 1.32, 'size': 37.5},
{'price': 1.31, 'size': 587.09},
{'price': 1.25, 'size': 3.0},
{'price': 1.13, 'size': 6.49},
{'price': 1.1, 'size': 32.0},
{'price': 1.03, 'size': 66.0},
{'price': 1.02, 'size': 15050.0},
{'price': 1.01, 'size': 1759.61}],
'availableToLay': [{'price': 3.05, 'size': 50.27},
{'price': 3.1, 'size': 222.38},
{'price': 3.15, 'size': 406.65},
{'price': 3.2, 'size': 122.67},
{'price': 3.25, 'size': 56.32},
{'price': 3.3, 'size': 69.86},
{'price': 3.35, 'size': 66.76},
{'price': 3.4, 'size': 204.27},
{'price': 3.45, 'size': 5.11},
{'price': 3.5, 'size': 27.02},
{'price': 3.55, 'size': 1.31},
{'price': 3.6, 'size': 2.46},
{'price': 3.7, 'size': 8.0},
{'price': 3.75, 'size': 181.81},
{'price': 3.8, 'size': 102.0},
{'price': 3.85, 'size': 132.0},
{'price': 3.9, 'size': 125.5},
{'price': 3.95, 'size': 50.0},
{'price': 4.0, 'size': 204.4},
{'price': 4.1, 'size': 161.0},
{'price': 4.2, 'size': 209.87},
{'price': 4.3, 'size': 134.0},
{'price': 4.4, 'size': 137.0},
{'price': 4.5, 'size': 106.0},
{'price': 4.6, 'size': 31.0},
{'price': 4.7, 'size': 1.89},
{'price': 4.8, 'size': 6.0},
{'price': 5.0, 'size': 6.0},
{'price': 5.1, 'size': 980.0},
{'price': 5.2, 'size': 16.0},
{'price': 5.4, 'size': 6.58},
{'price': 5.5, 'size': 3.0},
{'price': 6.2, 'size': 484.0},
{'price': 9.6, 'size': 1.31},
{'price': 29.0, 'size': 0.1},
{'price': 30.0, 'size': 2.0},
{'price': 100.0, 'size': 0.71},
{'price': 200.0, 'size': 50.0},
{'price': 330.0, 'size': 0.13},
{'price': 380.0, 'size': 0.15},
{'price': 880.0, 'size': 0.07},
{'price': 900.0, 'size': 0.21},
{'price': 1000.0, 'size': 12.0}],
'tradedVolume': [{'price': 2.82, 'size': 52.82},
{'price': 2.84, 'size': 510.91},
{'price': 2.86, 'size': 231.46},
{'price': 2.88, 'size': 576.84},
{'price': 2.9, 'size': 352.7},
{'price': 2.92, 'size': 1046.12},
{'price': 2.94, 'size': 1801.12},
{'price': 2.96, 'size': 684.53},
{'price': 2.98, 'size': 837.79},
{'price': 3.0, 'size': 1653.46},
{'price': 3.05, 'size': 1901.79},
{'price': 3.1, 'size': 976.5},
{'price': 3.15, 'size': 1372.35},
{'price': 3.2, 'size': 1152.81},
{'price': 3.25, 'size': 1258.86},
{'price': 3.3, 'size': 1238.7},
{'price': 3.35, 'size': 1421.73},
{'price': 3.4, 'size': 690.52},
{'price': 3.45, 'size': 617.1},
{'price': 3.5, 'size': 535.21},
{'price': 3.55, 'size': 13.53},
{'price': 3.6, 'size': 140.68},
{'price': 3.65, 'size': 57.06},
{'price': 3.7, 'size': 29.87},
{'price': 3.85, 'size': 11.31},
{'price': 3.95, 'size': 11.31},
{'price': 4.0, 'size': 40.42},
{'price': 4.1, 'size': 102.25},
{'price': 4.2, 'size': 629.99},
{'price': 4.3, 'size': 289.54},
{'price': 4.4, 'size': 372.96},
{'price': 4.5, 'size': 570.75},
{'price': 4.6, 'size': 21.38}]}
{'backStakeTaken': [{'price': 1.01, 'size': 784.54},
{'price': 3.0, 'size': 5.0},
{'price': 3.4, 'size': 8.0},
{'price': 3.5, 'size': 2.44},
{'price': 3.55, 'size': 60.0},
{'price': 4.0, 'size': 150.0}],
'farPrice': 2.56,
'layLiabilityTaken': [{'price': 1000.0, 'size': 988.15},
{'price': 4.0, 'size': 35.0},
{'price': 2.56, 'size': 600.3}],
'nearPrice': 2.993840265781219}

[The Edge]

Starting with a smaller example, I have this data

datetime: 2015-07-16T16:20:02.053510Z
version: 1028038019
marketId : 1.119512915
selectionId: 7318560

{'backStakeTaken': [{'price': 1.01, 'size': 148.01},
                    {'price': 4.0, 'size': 150.0},
                    {'price': 5.0, 'size': 5.0},
                    {'price': 9.0, 'size': 2.0}],
 'farPrice': 4.3995755158035355,
 'layLiabilityTaken': [{'price': 1000.0, 'size': 496.82},
                       {'price': 5.4, 'size': 600.3},
                       {'price': 4.0, 'size': 35.0}],
 'nearPrice': 6.460297754241303}

Starting with matching the back stake from 1.01 and the lay liability at 1000.0, my first estimate for the far price would be

4.356665090196609 = 1+( ( 496.82) / ( 148.01) )

However, there is 150.0 that would like to back the starting price at 4.0 or above. So my second estimate becomes

2.6671252642528778 = 1+( ( 496.82) / ( 148.01+150.0) )

However, 2.6<4.0, which means that not all the 4.0 will have been matched.

The amount matched would be:

17.60 = 496.82 / ( 4.0 - 1.0 ) - 148.01

So, from my calculations, the far price should be 4.0.

However, the data states that the far price is 4.3995755158035355. Where am I going wrong?