Baca csv ke dalam bait

editor php Xigua memperkenalkan anda kepada kaedah membaca fail CSV ke dalam bait. CSV ialah format data biasa yang biasa digunakan untuk menyimpan dan menukar data jadual. Kaedah tradisional ialah menggunakan fungsi operasi fail untuk membaca fail CSV baris demi baris dan menyimpannya sebagai tatasusunan atau objek. Walau bagaimanapun, dengan membaca fail CSV ke dalam bait, kami boleh memproses set data yang besar dengan lebih cekap dan lebih menjimatkan dari segi penggunaan memori. Kaedah ini boleh dilaksanakan dengan menggunakan fungsi fopen untuk membuka fail dalam mod binari dan menggunakan fungsi fread untuk membaca kandungan fail. Bait yang dibaca dalam boleh diproses selanjutnya menjadi tatasusunan atau struktur data lain untuk analisis dan manipulasi data. Melalui kaedah ini, kami boleh menggunakan fungsi PHP dengan lebih baik untuk memproses fail CSV dan meningkatkan kecekapan pemprosesan data.

Kandungan soalan

Saya menghadapi beberapa gelagat pelik semasa membaca fail csv ke dalam kepingan bait 2D. 42 baris pertama adalah baik, kemudian pengakhiran baris tambahan nampaknya dimasukkan ke dalam data yang mengacaukan keadaan:

Barisan pertama daripada 42 kali pertama:

row 0: 504921600000000000,truck_0,south,trish,h-2,v2.3,1500,150,12,52.31854,4.72037,124,0,221,0,25

Tambah baris pertama selepas baris 43:

row 0: 504921600000000000,truck_49,south,andy,f-150,v2.0,2000,200,15,38.9349,179.94282,289,0,269,0
row 1: 25

Kod minimum untuk menghasilkan semula masalah:

package main

import (
    "bufio"
    "log"
    "os"
)

type filedatasource struct {
    scanner *bufio.scanner
}

type batch struct {
    rows [][]byte
}

func (b *batch) len() uint {
    return uint(len(b.rows))
}

func (b *batch) append(row []byte) {
    b.rows = append(b.rows, row)
    for index, row := range b.rows {
        log.printf("row %d: %s\n", index, string(row))
    }
    if len(b.rows) > 43 {

        log.fatalf("asdf")
    }
}

type factory struct{}

func (f *factory) new() *batch {
    return &batch{rows: make([][]byte, 0)}
}

func main() {
    file, _ := os.open("/tmp/data1.csv")
    scanner := bufio.newscanner(bufio.newreadersize(file, 4<<20))
    b := batch{}

    for scanner.scan() {
        b.append(scanner.bytes())
    }
}

Csv yang saya gunakan:

504921600000000000,truck_0,South,Trish,H-2,v2.3,1500,150,12,52.31854,4.72037,124,0,221,0,25
504921600000000000,truck_1,South,Albert,F-150,v1.5,2000,200,15,72.45258,68.83761,255,0,181,0,25
504921600000000000,truck_2,North,Derek,F-150,v1.5,2000,200,15,24.5208,28.09377,428,0,304,0,25
504921600000000000,truck_3,East,Albert,F-150,v2.0,2000,200,15,18.11037,98.65573,387,0,192,0,25
504921600000000000,truck_4,West,Andy,G-2000,v1.5,5000,300,19,81.93919,56.12266,236,0,335,0,25
504921600000000000,truck_5,East,Seth,F-150,v2.0,2000,200,15,5.00552,114.50557,89,0,187,0,25
504921600000000000,truck_6,East,Trish,G-2000,v1.0,5000,300,19,41.59689,57.90174,395,0,150,0,25
504921600000000000,truck_8,South,Seth,G-2000,v1.0,5000,300,19,21.89157,44.58919,411,0,232,0,25
504921600000000000,truck_9,South,Andy,H-2,v2.3,1500,150,12,15.67271,112.4023,402,0,75,0,25
504921600000000000,truck_10,North,Albert,F-150,v2.3,2000,200,15,35.05682,36.20513,359,0,68,0,25
504921600000000000,truck_7,East,Andy,H-2,v2.0,1500,150,12,7.74826,14.96075,105,0,323,0,25
504921600000000000,truck_11,South,Derek,F-150,v1.0,2000,200,15,87.9924,134.71544,293,0,133,0,25
504921600000000000,truck_14,North,Albert,H-2,v1.0,1500,150,12,66.68217,105.76965,222,0,252,0,25
504921600000000000,truck_18,West,Trish,F-150,v2.0,2000,200,15,67.15164,153.56165,252,0,240,0,25
504921600000000000,truck_20,North,Rodney,G-2000,v2.0,5000,300,19,38.88807,65.86698,104,0,44,0,25
504921600000000000,truck_21,East,Derek,G-2000,v2.0,5000,300,19,81.87812,167.8083,345,0,327,0,25
504921600000000000,truck_22,West,Albert,G-2000,v1.5,5000,300,19,39.9433,16.0241,449,0,42,0,25
504921600000000000,truck_23,South,Andy,F-150,v2.0,2000,200,15,73.28358,98.05159,198,0,276,0,25
504921600000000000,truck_24,West,Rodney,G-2000,v2.3,5000,300,19,22.19262,0.27462,223,0,318,0,25
504921600000000000,truck_25,North,Trish,F-150,v2.0,2000,200,15,17.26704,16.91226,461,0,183,0,25
504921600000000000,truck_26,South,Seth,F-150,v1.5,2000,200,15,45.65327,144.60354,58,0,182,0,25
504921600000000000,truck_12,East,Trish,G-2000,v1.0,5000,300,19,36.03928,113.87118,39,0,294,0,25
504921600000000000,truck_13,West,Derek,H-2,v1.0,1500,150,12,14.07479,110.77267,152,0,69,0,25
504921600000000000,truck_27,West,Seth,G-2000,v1.5,5000,300,19,79.55971,97.86182,252,0,345,0,25
504921600000000000,truck_28,West,Rodney,G-2000,v1.5,5000,300,19,60.33457,4.62029,74,0,199,0,25
504921600000000000,truck_16,South,Albert,G-2000,v1.5,5000,300,19,51.16438,121.32451,455,0,290,0,25
504921600000000000,truck_19,West,Derek,G-2000,v1.5,5000,300,19,19.69355,139.493,451,0,300,0,25
504921600000000000,truck_31,North,Albert,G-2000,v1.0,5000,300,19,0.75251,116.83474,455,0,49,0,25
504921600000000000,truck_32,West,Seth,F-150,v2.0,2000,200,15,4.07566,164.43909,297,0,277,0,25
504921600000000000,truck_33,West,Rodney,G-2000,v1.5,5000,300,19,89.19448,10.47499,407,0,169,0,25
504921600000000000,truck_34,West,Rodney,G-2000,v2.0,5000,300,19,73.7383,10.79582,488,0,170,0,25
504921600000000000,truck_35,West,Seth,G-2000,v2.3,5000,300,19,60.02428,2.51011,480,0,307,0,25
504921600000000000,truck_36,North,Andy,G-2000,v1.0,5000,300,19,87.52877,45.07308,161,0,128,0,25
504921600000000000,truck_38,West,Andy,H-2,v2.3,,150,12,63.54604,119.82031,282,0,325,0,25
504921600000000000,truck_39,East,Derek,G-2000,v1.5,5000,300,19,33.83548,3.90996,294,0,123,0,25
504921600000000000,truck_40,West,Albert,H-2,v2.0,1500,150,12,32.32773,118.43138,276,0,316,0,25
504921600000000000,truck_41,East,Rodney,F-150,v1.0,2000,200,15,68.85572,173.23123,478,0,207,0,25
504921600000000000,truck_42,West,Trish,F-150,v2.0,2000,200,15,38.45195,171.2884,113,0,180,0,25
504921600000000000,truck_43,East,Derek,H-2,v2.0,1500,150,12,52.90189,49.76966,295,0,195,0,25
504921600000000000,truck_44,South,Seth,H-2,v1.0,1500,150,12,32.33297,3.89306,396,0,320,0,25
504921600000000000,truck_30,East,Andy,G-2000,v1.5,5000,300,19,29.62198,83.73482,291,0,267,0,25
504921600000000000,truck_46,West,Seth,H-2,v2.3,1500,150,12,26.07966,118.49629,321,,267,0,25
504921600000000000,truck_37,South,Andy,G-2000,v2.0,5000,300,19,57.90077,77.20136,77,0,179,0,25
504921600000000000,truck_49,South,Andy,F-150,v2.0,2000,200,15,38.9349,179.94282,289,0,269,0,25
504921600000000000,truck_53,West,Seth,G-2000,v2.3,5000,300,19,25.02,157.45082,272,0,5,0,25
504921600000000000,truck_54,North,Andy,H-2,v2.0,1500,150,12,87.62736,106.0376,360,0,66,0,25
504921600000000000,truck_55,East,Albert,G-2000,v1.0,5000,300,19,78.56605,71.16225,295,0,150,0,25
504921600000000000,truck_56,North,Derek,F-150,v2.0,2000,200,15,23.51619,123.22682,71,0,209,0,25
504921600000000000,truck_57,South,Rodney,F-150,v2.3,2000,200,15,26.07996,159.92716,454,0,22,0,25
504921600000000000,truck_58,South,Derek,F-150,v2.0,2000,200,15,84.79333,79.23813,175,0,246,0,25
504921600000000000,truck_59,East,Andy,H-2,v2.0,1500,150,12,8.7621,82.48318,82,0,55,0,25
504921600000000000,truck_45,East,Trish,G-2000,v1.0,5000,300,19,17.48624,100.78121,306,0,193,0,25
504921600000000000,truck_47,South,Derek,G-2000,v1.5,5000,300,19,41.62173,110.80422,111,0,78,0,25
504921600000000000,truck_48,East,Trish,G-2000,v1.5,5000,300,19,63.90773,141.50555,53,0,,0,25
504921600000000000,truck_50,East,Andy,H-2,v2.3,1500,150,12,45.44111,172.39833,219,0,88,0,25
504921600000000000,truck_51,East,Rodney,F-150,v2.3,2000,200,15,89.03645,91.57675,457,0,337,0,25
504921600000000000,truck_52,West,Derek,G-2000,v1.0,5000,300,19,89.0133,97.8037,23,0,168,0,25
504921600000000000,truck_61,East,Albert,G-2000,v2.3,5000,300,19,75.91676,167.78366,462,0,60,0,25
504921600000000000,truck_62,East,Derek,H-2,v1.5,1500,150,12,54.61668,103.21398,231,0,143,0,25
504921600000000000,truck_63,South,Rodney,H-2,v2.0,1500,150,12,37.13702,149.25546,46,0,118,0,25
504921600000000000,truck_64,South,Albert,G-2000,v2.0,5000,300,19,45.04214,10.73002,447,0,253,0,25
504921600000000000,truck_60,South,Derek,H-2,v1.5,1500,150,12,57.99184,33.45994,310,0,93,0,25
504921600000000000,truck_67,South,Seth,H-2,v1.0,1500,150,12,4.62985,155.01707,308,0,22,0,25
504921600000000000,truck_68,West,Rodney,F-150,v1.5,2000,200,15,16.90741,123.03863,303,0,43,0,25
504921600000000000,truck_69,East,Derek,H-2,v2.3,1500,150,12,79.88424,120.79121,407,0,138,0,25
504921600000000000,truck_70,North,Albert,H-2,v2.0,1500,150,12,77.87592,164.70924,270,0,21,0,25
504921600000000000,truck_71,West,Seth,G-2000,v2.3,5000,300,19,72.75635,78.0365,391,0,32,0,25
504921600000000000,truck_73,North,Seth,F-150,v1.5,2000,200,15,37.67468,91.09732,489,0,103,0,25
504921600000000000,truck_74,North,Trish,H-2,v1.0,1500,150,12,41.4456,158.13897,206,0,79,0,25
504921600000000000,truck_75,South,Andy,F-150,v1.5,2000,200,15,4.11709,175.65994,378,0,176,0,25
504921600000000000,truck_66,South,Seth,G-2000,v2.0,5000,300,19,42.24286,151.8978,227,0,67,0,25
504921600000000000,truck_72,South,Andy,G-2000,v2.3,5000,300,19,82.46228,2.44504,487,0,39,0,25
504921600000000000,truck_76,South,Rodney,F-150,v2.3,2000,200,15,71.62798,121.89842,283,0,164,0,25
504921600000000000,truck_78,South,Seth,F-150,v2.0,2000,200,15,13.96218,39.04615,433,0,326,0,25
504921600000000000,truck_79,South,Andy,G-2000,v2.0,5000,300,19,56.54137,,46,0,127,0,25
504921600000000000,truck_81,West,Rodney,G-2000,v2.3,5000,300,19,59.42624,115.59744,68,0,296,0,25
504921600000000000,truck_83,South,Albert,F-150,v2.0,2000,200,15,49.20261,115.98262,449,0,132,0,25
504921600000000000,truck_84,West,Derek,H-2,v1.0,1500,150,12,70.16476,59.05399,301,0,134,0,25
504921600000000000,truck_85,West,Derek,G-2000,v1.0,5000,300,19,11.75251,142.86513,358,0,339,0,25
504921600000000000,truck_86,West,Rodney,G-2000,v1.0,5000,300,19,30.92821,127.53274,367,0,162,0,25
504921600000000000,truck_87,West,Rodney,H-2,v2.0,1500,150,12,32.86913,155.7666,122,0,337,0,25
504921600000000000,truck_88,West,Andy,G-2000,v1.5,5000,300,19,60.03367,9.5707,204,0,333,0,25
504921600000000000,truck_80,East,Andy,G-2000,v2.3,5000,300,,46.13937,137.42962,295,0,290,0,25
504921600000000000,truck_91,East,Derek,F-150,v2.0,2000,200,15,7.13401,52.78885,100,0,147,0,25
504921600000000000,truck_93,North,Derek,G-2000,v2.0,5000,300,19,11.46065,20.57173,242,0,148,0,25
504921600000000000,truck_94,North,Derek,F-150,v1.0,2000,200,15,59.53287,26.98247,427,0,341,0,25
504921600000000000,truck_95,East,Albert,G-2000,v2.0,5000,300,19,37.31513,134.40078,383,0,121,0,25
504921600000000000,truck_96,East,Albert,G-2000,v1.5,5000,300,19,15.78803,146.68255,348,0,189,0,25
504921600000000000,truck_97,South,Seth,F-150,v1.0,2000,200,15,14.08559,18.49763,369,0,34,0,25
504921600000000000,truck_98,South,Albert,G-2000,v1.5,5000,300,19,15.1474,71.85194,89,0,238,0,25
504921600000000000,truck_77,East,Trish,F-150,v2.0,2000,200,15,80.5734,17.68311,389,0,218,0,25
504921600000000000,truck_82,West,Derek,H-2,v2.0,1500,150,12,57.00976,90.13642,102,0,296,0,25
504921600000000000,truck_92,North,Derek,H-2,v1.0,1500,150,12,54.40335,153.5809,123,0,150,0,25
504921600000000000,truck_99,West,Trish,G-2000,v1.5,5000,300,19,62.73061,26.1884,309,0,202,0,25
504921610000000000,truck_1,South,Albert,F-150,v1.5,2000,200,15,72.45157,68.83919,259,0,180,2,27.5
504921610000000000,truck_2,North,Derek,F-150,v1.5,2000,200,15,24.5195,28.09369,434,6,302,0,22.1
504921610000000000,truck_3,East,Albert,F-150,v2.0,2000,200,15,18.107,98.66002,390,,190,0,21.2
504921610000000000,truck_4,West,Andy,G-2000,v1.5,5000,300,19,81.9438,56.12717,244,8,334,2,27.6
504921610000000000,truck_5,East,Seth,F-150,v2.0,2000,200,15,5.00695,114.50676,92,7,183,2,28.5
504921610000000000,truck_6,East,Trish,G-2000,v1.0,5000,300,19,41.59389,57.90166,403,0,149,0,22.7
504921610000000000,truck_7,East,Andy,H-2,v2.0,1500,150,12,7.74392,14.95756,,0,320,0,28.2
504921610000000000,truck_12,East,Trish,G-2000,v1.0,5000,300,19,36.03979,113.8752,34,0,293,1,26.3
504921610000000000,truck_13,West,Derek,H-2,v1.0,1500,150,12,14.07315,110.77235,150,0,72,,21.9
504921610000000000,truck_14,North,Albert,H-2,v1.0,1500,150,12,,105.76727,218,5,253,1,21.9
504921610000000000,truck_15,South,Albert,H-2,v1.5,1500,150,12,6.78254,166.86685,5,0,110,0,26.3
504921610000000000,truck_16,South,Albert,G-2000,v1.5,5000,300,19,51.16405,121.32556,445,0,294,3,29.9
504921610000000000,truck_17,West,Derek,H-2,v1.5,1500,150,12,8.12913,56.57343,9,0,6,4,29
504921610000000000,truck_18,West,Trish,F-150,v2.0,2000,200,15,67.15167,153.56094,260,1,239,1,23.3
504921610000000000,truck_19,West,Derek,G-2000,v1.5,5000,300,19,19.69456,139.49545,448,4,298,0,29.9
504921610000000000,truck_20,North,Rodney,G-2000,v2.0,5000,300,19,38.88968,65.86504,103,0,41,1,23.6
504921610000000000,truck_21,East,Derek,G-2000,v2.0,5000,300,19,81.88232,167.81287,345,0,326,0,20.8
504921610000000000,truck_0,South,Trish,H-2,v2.3,1500,150,12,52.32335,4.71786,128,9,225,0,25.8
504921610000000000,truck_22,West,Albert,G-2000,v1.5,5000,300,19,39.94345,16.02353,440,1,45,0,27.8
504921610000000000,truck_8,South,Seth,G-2000,v1.0,5000,300,19,21.89464,44.58628,402,0,234,0,20.3
504921610000000000,truck_23,South,Andy,F-150,v2.0,2000,200,15,73.28131,98.05635,201,7,277,0,25.3
504921610000000000,truck_24,West,Rodney,G-2000,v2.3,5000,300,19,22.19506,0.27702,217,0,321,2,29.5
504921610000000000,truck_9,South,Andy,H-2,v2.3,1500,150,12,,112.40429,402,9,75,4,29.5
504921610000000000,truck_26,South,Seth,F-150,v1.5,2000,200,15,45.65798,144.60844,59,1,183,0,21.7
504921610000000000,truck_27,West,Seth,G-2000,v1.5,5000,300,19,79.55699,97.86561,255,7,348,2,20.2
504921610000000000,truck_25,North,Trish,F-150,v2.0,2000,200,15,17.26506,16.91691,453,8,186,0,24.3
504921610000000000,truck_28,West,Rodney,G-2000,v1.5,5000,300,19,60.33272,4.61578,84,3,198,0,23.1
504921610000000000,truck_29,East,Rodney,G-2000,v2.0,5000,300,19,80.30331,146.54254,340,5,118,0,25.6
504921610000000000,truck_30,East,Andy,G-2000,v1.5,5000,300,19,29.62434,83.73246,300,0,270,4,22.3
504921610000000000,truck_33,West,Rodney,G-2000,v1.5,5000,300,19,89.19593,10.47733,403,8,170,0,29.6
504921610000000000,truck_36,North,Andy,G-2000,v1.0,5000,300,19,87.53087,45.07276,163,0,132,1,27.6

Saya menjangkakan baris[][]bait mengandungi data csv baris demi baris

Penyelesaian

Seperti yang telah dicadangkan, anda harus menggunakan encoding/csv.

Iaitu, punca masalah anda adalah pada godoc di atas fungsi bytes():

// bytes returns the most recent token generated by a call to scan.
// the underlying array may point to data that will be overwritten
// by a subsequent call to scan. it does no allocation.
func (s *scanner) bytes() []byte {
    return s.token
}

Oleh itu, panggilan seterusnya scan() boleh mengubah suai kepingan bait yang dikembalikan. Untuk mengelakkan ini, anda perlu menyalin kepingan bait seperti

for scanner.Scan() {
    row := scanner.Bytes()
    bs := make([]byte, len(row))
    copy(bs, row)
    b.Append(bs)
}

Atas ialah kandungan terperinci Baca csv ke dalam bait. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!