PythonのpandasでDataFrameから複数の行を選択する

pandas の DataFrame から複数行を選択するには loc を使う。

import pandas as pd

df = pd.read_csv('population.csv', index_col=0)
rows = df.loc[['目黒区', '品川区']]
print(rows)

結果はこうなる。

          世帯数       総数        男        女    人口密度
市区町村                                            
目黒区   156,583  279,342  132,206  147,136  19,042
品川区   220,678  394,700  193,644  201,056  17,281

ここで population.csv には下のデータが入っている。

市区町村,世帯数,総数,男,女,人口密度
千代田区,"35,830","63,635","31,935","31,700","5,458"
中央区,"91,852","162,502","77,241","85,261","15,916"
港　区,"145,865","257,426","121,326","136,100","12,638"
新宿区,"219,639","346,162","173,743","172,419","18,999"
文京区,"121,128","221,489","105,462","116,027","19,618"
台東区,"118,858","199,292","101,917","97,375","19,712"
墨田区,"150,855","271,859","134,678","137,181","19,743"
江東区,"267,262","518,479","256,116","262,363","12,910"
品川区,"220,678","394,700","193,644","201,056","17,281"
目黒区,"156,583","279,342","132,206","147,136","19,042"
大田区,"391,146","729,534","362,653","366,881","11,993"
世田谷区,"479,792","908,907","431,026","477,881","15,657"
渋谷区,"137,582","226,594","108,768","117,826","14,996"
中野区,"204,613","331,658","167,378","164,280","21,274"
杉並区,"321,531","569,132","273,057","296,075","16,710"
豊島区　,"179,880","289,508","145,334","144,174","22,253"
北　区,"196,580","351,976","174,910","177,066","17,078"
荒川区,"115,944","215,966","107,283","108,683","21,256"
板橋区,"309,133","566,890","278,662","288,228","17,594"
練馬区,"370,567","732,433","356,279","376,154","15,234"
足立区,"346,739","688,512","345,291","343,221","12,930"
葛飾区,"233,158","462,591","231,272","231,319","13,293"
江戸川区,"342,016","698,031","351,914","346,117","13,989"
八王子市,"267,736","562,460","281,506","280,954","3,018"
立川市,"91,270","183,822","91,460","92,362","7,546"
武蔵野市,"76,765","146,399","70,120","76,279","13,333"
三鷹市,"93,665","187,199","91,624","95,575","11,401"
青梅市,"63,142","134,086","67,393","66,693","1,298"
府中市,"125,060","260,011","130,582","129,429","8,835"
昭島市,"53,827","113,215","56,384","56,831","6,529"
調布市,"118,804","235,169","114,909","120,260","10,898"
町田市,"195,643","428,685","209,971","218,714","5,991"
小金井市,"60,367","121,443","59,955","61,488","10,747"
小平市,"91,602","193,596","95,312","98,284","9,439"
日野市,"88,402","185,393","92,983","92,410","6,729"
東村山市,"72,676","150,789","73,621","77,168","8,797"
国分寺市,"60,111","123,689","60,901","62,788","10,793"
国立市,"37,728","76,038","37,161","38,877","9,330"
福生市,"30,506","58,243","29,132","29,111","5,733"
狛江市,"42,157","82,481","40,005","42,476","12,908"
東大和市,"38,852","85,565","42,208","43,357","6,376"
清瀬市,"35,454","74,737","36,092","38,645","7,306"
東久留米市,"54,257","116,896","57,066","59,830","9,076"
武蔵村山市,"31,640","72,546","36,177","36,369","4,735"
多摩市,"71,851","148,745","72,927","75,818","7,080"
稲城市,"39,991","90,585","45,589","44,996","5,041"
羽村市,"25,718","55,607","28,251","27,356","5,617"
あきる野市,"35,519","80,851","40,304","40,547","1,100"
西東京市,"97,350","202,817","98,839","103,978","12,877"
瑞穂町,"14,912","33,213","16,922","16,291","1,971"
日の出町,"7,383","16,732","8,224","8,508",596
檜原村,"1,181","2,217","1,100","1,117",21
奥多摩町,"2,685","5,179","2,601","2,578",23
大島町,"4,635","7,716","3,971","3,745",85
利島村,174,323,175,148,78
新島村,"1,381","2,722","1,325","1,397",99
神津島村,917,"1,898",975,923,102
三宅村,"1,620","2,481","1,356","1,125",45
御蔵島村,170,317,167,150,15
八丈町,"4,365","7,465","3,720","3,745",103
青ヶ島村,109,159,92,67,27
小笠原村,"1,492","2,625","1,451","1,174",25

引用：住民基本台帳による東京都の世帯と人口（町丁別・年齢別）

pandas の read_csv はファイルの内容を DataFrame にする。読み込んだ DataFrame の loc に行の名前をリストで入れると、その行のデータが出力される。

read_csv のオプションに index_col=0 がある。これは読み込む DataFrame に 0 から始まる整数値のインデックスを与えないことを意味する（正確さは欠ける）。