Aidemy Python入門 - Note for Machine Learning

Aidemy Python入門

lambda式

無名関数の作成

code:Python

a = 4

def func1(a):

return 2*(a**2)-3*a+1

func2 = lambda a: 2*(a**2)-3*a+1

print(func1(a))

print(func2(a))

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lambdaによる計算

code: Python

x = 5

y = 6

z = 2

def func3(x, y, z):

return x*y+z

func4 = lambda x, y, z: x*y+z

# 出力

print(func3(x, y, z))

print(func4(x, y, z))

--------------------------------------------------------------------------

ifを用いたlambda

code: Python

a1 = 13

a2 = 32

func5 = lambda a: a ** 2 - 40 * a + 350 if 10 <= a < 30 else 50

print(func5(a1))

print(func5(a2))

--------------------------------------------------------------------------

-1

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リスト内包括

listの分割（split）

code: Python

self_data = "My name is Yamada"

list = self_data.split(" ")

print(list3)

--------------------------------------------------------------------------

Yamada

--------------------------------------------------------------------------

listの分割（re.split）

code: Python

import re

time_data = "2017/4/1_22:15"

list = re.split("/_:", time_data)

print(list1)

print(list3)

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高階関数（map）

code: Python

import re

time_list = [

"2006/11/26_2:40",

"2009/1/16_23:35",

"2014/5/4_14:26",

"2017/8/9_7:5",

"2017/4/1_22:15"

]

# 文字列から"時"を取り出す関数

def getHour(data):

time_list = re.split("/_:", data)

return int(time_list3)

# lambda式なら

# getHour = lambda data: re.split("/_:", data)3

hour_list = list(map(getHour, time_list))

print(hour_list)

--------------------------------------------------------------------------

2, 23, 14, 7, 22

--------------------------------------------------------------------------

filter

code: Python

import re

time_list = [

"2006/11/26_2:40",

"2009/1/16_23:35",

"2014/5/4_14:26",

"2017/8/9_7:5",

"2017/4/1_22:15"

]

# 文字列の"月"が条件を満たすときにTrueを返す関数

get_month_one_to_six = lambda data: 1 <= int(re.split("/_:", data)1) <= 6

month_list = list(filter(get_month_one_to_six, time_list))

print(month_list)

--------------------------------------------------------------------------

'2009/1/16_23:35', '2014/5/4_14:26', '2017/4/1_22:15'

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sorted

code: Python

# time_data...年, 月, 日, 時, 分

time_data = [

]

# "時"をキーとしてソートする

list = sorted(time_data, key=lambda x: x3)

print(list)

--------------------------------------------------------------------------

2006, 11, 26, 2, 40], 2017, 8, 9, 7, 5, 2014, 5, 4, 14, 26, 2017, 4, 1, 22, 15, [2009, 1, 16, 23, 35

--------------------------------------------------------------------------

リストの生成

code: Python

# minute_data、単位は分

minute_data = 30, 155, 180, 74, 11, 60, 82

# 分を時, 分に換算する関数

h_m_split = lambda x: x // 60, x % 60

# リスト内包表記

h_m_data = h_m_split(x) for x in minute_data

print(h_m_data)

--------------------------------------------------------------------------

0, 30], 2, 35, 3, 0, 1, 14, 0, 11, 1, 0, [1, 22

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if文を用いたループ

code: Python

# minute_data、単位は分

minute_data = 30, 155, 180, 74, 11, 60, 82

# リスト内包表記

just_hour_data = x for x in minute_data if x % 60 == 0

print(just_hour_data)

--------------------------------------------------------------------------

180, 60

--------------------------------------------------------------------------

複数配列の同時ループ

code: Python

# 時間データhour, 分データminute

hour = 0, 2, 3, 1, 0, 1, 1

minute = 30, 35, 0, 14, 11, 0, 22

# 時, 分を引数に、分に換算する関数

convert_to_minute = lambda hour, minute: hour * 60 + minute

# リスト内包表記

minute_data = convert_to_minute(hour, minute) for hour, minute in zip(hour, minute)

print(minute_data)

--------------------------------------------------------------------------

30, 155, 180, 74, 11, 60, 82

--------------------------------------------------------------------------

多重ループ

code: Python

# 二進数の桁

fours_place = 0, 1

twos_place = 0, 1

ones_place = 0, 1

# リスト内包表記の多重ループを用いて0から7までの整数を配列に

digit = x*4 + y*2 + z for x in fours_place for y in twos_place for z in ones_place

print(digit)

--------------------------------------------------------------------------

0, 1, 2, 3, 4, 5, 6, 7

--------------------------------------------------------------------------

辞書オブジェクト

defaultdict

code: Python

from collections import defaultdict

# 文字列description

description = \

"Artificial intelligence (AI, also machine intelligence, MI) is " + \

"intelligence exhibited by machines, rather than " + \

"humans or other animals (natural intelligence, NI)."

# defaultdictを定義

char_freq = defaultdict(int)

# 文字の出現回数を記録

for i in description:

char_freqi += 1

# ソートし、上位10要素を出力

# sorted関数は、sorted(ソート対象、ソートに使うkey、ソートオプション）で呼び出す

# ソートオプションはreverse=Trueで降順に

# ソートに使うkeyはitemsを指定して（アルファベット、出現回数）のリスト形式で取り出し、lambdaで「リストの二番目」、つまり出現回数を、x1として指定

print(sorted(char_freq.items(), key=lambda x: x1, reverse=True):10)

--------------------------------------------------------------------------

', 20), ('e', 18), ('i', 17), ('n', 14), ('l', 12), ('a', 11), ('t', 10), ('c', 7), ('h', 7), ('r', 6)

--------------------------------------------------------------------------

value内の要素の追加

code: Python

from collections import defaultdict

# まとめたいデータprice

price = [

("apple", 50),

("banana", 120),

("grape", 500),

("apple", 70),

("lemon", 150),

("grape", 1000)

]

# defaultdictを定義

d = defaultdict(list)

# 上記の例と同様にvalueの要素に値段を追加

for key, value in price:

dkey.append(value)

# 各valueの平均値を計算し、配列にして出力

print(sum(x) / len(x) for x in d.values())

--------------------------------------------------------------------------

60.0, 120.0, 750.0, 150.0

--------------------------------------------------------------------------

Counter

code: Python

from collections import Counter

# 文字列description

description = \

"Artificial intelligence (AI, also machine intelligence, MI) is " + \

"intelligence exhibited by machines, rather than " + \

"humans or other animals (natural intelligence, NI)."

# Counterを定義

char_freq = Counter(description)

# ソートし、上位10要素を出力

print(char_freq.most_common(10))

--------------------------------------------------------------------------

', 20), ('e', 18), ('i', 17), ('n', 14), ('l', 12), ('a', 11), ('t', 10), ('c', 7), ('h', 7), ('r', 6)

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