Pythonの辞書機能

Pythonには辞書（dictionary）という機能がある．辞書はリストに似た存在であり，{key:value}のペアでリスト化されていて，キーを参照すると，その値が返されるというものである．

化学分野での利用

自分の専門分野役に立つ利用法がないか考えてみた．まず，思いついたのは「原子番号」と「元素記号」の対応である．

元素記号と原子番号をカンマ区切りで記録したファイル（下表左）をオープンして，辞書を作成するためのプログラムをプログラミング練習を兼ねて書いてみた（下表右）．

ファイルに書き出すまでもないので，IDLEのシェルに書き出される結果をコピーペーストして，以下のプログラムを作った．辞書形式のデータを貼り付けて，そのデータを読み出すだけの処理である．プリント文の括弧内に記載されているように指定するとそれぞれの評価結果が表示される．

プログラム

dic_atom={" H " : 1 ," He " : 2 ," Li " : 3 ," Be " : 4 ," B " : 5 ," C " : 6 ," N " : 7 ," O " : 8 ," F " : 9 ," Ne " : 10 ," Na " : 11 ," Mg " : 12 ," Al " : 13 ," Si " : 14 ," P " : 15 ," S " : 16 ," Cl " : 17 ," Ar " : 18 ," K " : 19 ," Ca " : 20 ," Sc " : 21 ," Ti " : 22 ," V " : 23 ," Cr " : 24 ," Mn " : 25 ," Fe " : 26 ," Co " : 27 ," Ni " : 28 ," Cu " : 29 ," Zn " : 30 ," Ga " : 31 ," Ge " : 32 ," As " : 33 ," Se " : 34 ," Br " : 35 ," Kr " : 36 ," Rb " : 37 ," Sr " : 38 ," Y " : 39 ," Zr " : 40 ," Nb " : 41 ," Mo " : 42 ," Tc " : 43 ," Ru " : 44 ," Rh " : 45 ," Pd " : 46 ," Ag " : 47 ," Cd " : 48 ," In " : 49 ," Sn " : 50 ," Sb " : 51 ," Te " : 52 ," I " : 53 ," Xe " : 54 ," Cs " : 55 ," Ba " : 56 ," La " : 57 ," Ce " : 58 ," Pr " : 59 ," Nd " : 60 ," Pm " : 61 ," Sm " : 62 ," Eu " : 63 ," Gd " : 64 ," Tb " : 65 ," Dy " : 66 ," Ho " : 67 ," Er " : 68 ," Tm " : 69 ," Yb " : 70 ," Lu " : 71 ," Hf " : 72 ," Ta " : 73 ," W " : 74 ," Re " : 75 ," Os " : 76 ," Ir " : 77 ," Pt " : 78 ," Au " : 79 ," Hg " : 80 ," Tl " : 81 ," Pb " : 82 ," Bi " : 83 ," Po " : 84 ," At " : 85 ," Rn " : 86 ," Fr " : 87 ," Ra " : 88 ," Ac " : 89 ," Th " : 90 ," Pa " : 91 ," U " : 92 ," Np " : 93 ," Pu " : 94 ," Am " : 95 ," Cm " : 96 ," Bk " : 97 ," Cf " : 98 ," Es " : 99 ," Fm " : 100 ," Md " : 101 ," No " : 102 ," Lr " : 103 ," Rf " : 104 ," Db " : 105 ," Sg " : 106 ," Bh " : 107 ," Hs " : 108 ," Mt " : 109 ," Ds " : 110 ," Rg " : 111 ," Cn " : 112 }

print (len(dic_atom)) ⬅ 個数

print (dic_atom.keys()) ⬅ キーのリストを表示

print (dic_atom.values()) ⬅ バリューの表示

print (dic_atom[" Au "] ) ⬅ Au（金）の原子番号

実行結果

112

dict_keys([' H ', ' He ', ' Li ', ' Be ', ' B ', ' C ', ' N ', ' O ', ' F ', ' Ne ', ' Na ', ' Mg ', ' Al ', ' Si ', ' P ', ' S ', ' Cl ', ' Ar ', ' K ', ' Ca ', ' Sc ', ' Ti ', ' V ', ' Cr ', ' Mn ', ' Fe ', ' Co ', ' Ni ', ' Cu ', ' Zn ', ' Ga ', ' Ge ', ' As ', ' Se ', ' Br ', ' Kr ', ' Rb ', ' Sr ', ' Y ', ' Zr ', ' Nb ', ' Mo ', ' Tc ', ' Ru ', ' Rh ', ' Pd ', ' Ag ', ' Cd ', ' In ', ' Sn ', ' Sb ', ' Te ', ' I ', ' Xe ', ' Cs ', ' Ba ', ' La ', ' Ce ', ' Pr ', ' Nd ', ' Pm ', ' Sm ', ' Eu ', ' Gd ', ' Tb ', ' Dy ', ' Ho ', ' Er ', ' Tm ', ' Yb ', ' Lu ', ' Hf ', ' Ta ', ' W ', ' Re ', ' Os ', ' Ir ', ' Pt ', ' Au ', ' Hg ', ' Tl ', ' Pb ', ' Bi ', ' Po ', ' At ', ' Rn ', ' Fr ', ' Ra ', ' Ac ', ' Th ', ' Pa ', ' U ', ' Np ', ' Pu ', ' Am ', ' Cm ', ' Bk ', ' Cf ', ' Es ', ' Fm ', ' Md ', ' No ', ' Lr ', ' Rf ', ' Db ', ' Sg ', ' Bh ', ' Hs ', ' Mt ', ' Ds ', ' Rg ', ' Cn '])

dict_values([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112])

79

プログラムの冒頭に多量の配列データを記載するのは見苦しいので，JSONファイルに保存して利用する方式にした．

辞書管理：JSONファイルの利用

JSONとはJavaScript Object Notationの略で，JavaScriptの書き方に従って書かれたデータファイルである．Pythonで使用するためには変換する必要があり，そのための関数が準備されている．

JSONファイルへの書き出し

Pythonディクショナリはjsonモジュールを使ってJSONファイルに保存できる．保存の際はdumpメソッドを用いる．辞書（dictatom）をatomnum.jsonのファイル名で保存する．

プログラム

import json

dictatom={" H " : 1 ," He " : 2 ," Li " : 3 ," Be " : 4 ," B " : 5 ," C " : 6 ," N " : 7 ," O " : 8 ," F " : 9 ," Ne " : 10 ," Na " : 11 ," Mg " : 12 ," Al " : 13 ," Si " : 14 ," P " : 15 ," S " : 16 ," Cl " : 17 ," Ar " : 18 ," K " : 19 ," Ca " : 20 ," Sc " : 21 ," Ti " : 22 ," V " : 23 ," Cr " : 24 ," Mn " : 25 ," Fe " : 26 ," Co " : 27 ," Ni " : 28 ," Cu " : 29 ," Zn " : 30 ," Ga " : 31 ," Ge " : 32 ," As " : 33 ," Se " : 34 ," Br " : 35 ," Kr " : 36 ," Rb " : 37 ," Sr " : 38 ," Y " : 39 ," Zr " : 40 ," Nb " : 41 ," Mo " : 42 ," Tc " : 43 ," Ru " : 44 ," Rh " : 45 ," Pd " : 46 ," Ag " : 47 ," Cd " : 48 ," In " : 49 ," Sn " : 50 ," Sb " : 51 ," Te " : 52 ," I " : 53 ," Xe " : 54 ," Cs " : 55 ," Ba " : 56 ," La " : 57 ," Ce " : 58 ," Pr " : 59 ," Nd " : 60 ," Pm " : 61 ," Sm " : 62 ," Eu " : 63 ," Gd " : 64 ," Tb " : 65 ," Dy " : 66 ," Ho " : 67 ," Er " : 68 ," Tm " : 69 ," Yb " : 70 ," Lu " : 71 ," Hf " : 72 ," Ta " : 73 ," W " : 74 ," Re " : 75 ," Os " : 76 ," Ir " : 77 ," Pt " : 78 ," Au " : 79 ," Hg " : 80 ," Tl " : 81 ," Pb " : 82 ," Bi " : 83 ," Po " : 84 ," At " : 85 ," Rn " : 86 ," Fr " : 87 ," Ra " : 88 ," Ac " : 89 ," Th " : 90 ," Pa " : 91 ," U " : 92 ," Np " : 93 ," Pu " : 94 ," Am " : 95 ," Cm " : 96 ," Bk " : 97 ," Cf " : 98 ," Es " : 99 ," Fm " : 100 ," Md " : 101 ," No " : 102 ," Lr " : 103 ," Rf " : 104 ," Db " : 105 ," Sg " : 106 ," Bh " : 107 ," Hs " : 108 ," Mt " : 109 ," Ds " : 110 ," Rg " : 111 ," Cn " : 112 }

with open('atomnum.json', 'w') as f:

json.dump(dictatom, f)

JSONファイルの読み込み

JSONファイルの読み込みは，jsonモジュールのloadメソッドを使う．

プログラム中に辞書を内蔵させてもよいが，別ファイルにしてloadするようにすれば，プログラムがスッキリとする．

プログラム

import json

with open('atomnum.json') as f:

dictatom = json.load(f)

print (len(dictatom))

print (dictatom[" Au "] )

このプログラムを実行すると以下の結果が得られる．

112 ⬅ 個数

79 ⬅ Au（金）の原子番号

会話型プログラム

import json

with open('atomnum.json') as f:

dictatom = json.load(f)

while True:

atn = input('atomic symbol?')

atn = " "+atn+" "

if atn == ' q ':

break

else:

print(dictatom[atn])

実行結果

atomic symbol?S

16

atomic symbol?Cｌ

1７

atomic symbol?q ⬅ qで終了

参考資料

Python入門 辞書

CSV ファイルの読み書き

リストから辞書を作成