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最近はC言語ばっかりでしたが、今後もソフトウェア屋をやるのであればPythonかRubyは慣れておきたいところ。Pythonを新たに始めるならPython3一択らしい(Python2は必要になったら調べれば事足りるため)。個人的に新しい言語を覚えるときは短いサンプルコードを見て作るのが一番早いので簡単なものからはじめてみた。
目次
Python3のインストール
まずはPython3のインストールから。Linux環境(CentOS7)に下記のソースコード(tarball)をダウンロード後、ビルドしてインストールする。
https://www.python.org/downloads/source/
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[user@localhost ~]$ sudo yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gcc [user@localhost Download]$ wget https://www.python.org/ftp/python/3.4.7/Python-3.4.7.tgz [user@localhost Download]]$ tar zxvf Python-3.4.7.tgz [user@localhost Python-3.4.7]$ cd Python-3.4.7 [user@localhost Python-3.4.7]$ ./configure [user@localhost Python-3.4.7]$ make [user@localhost Python-3.4.7]$ sudo make install [user@localhost Python-3.4.7]$ sudo ln -s /usr/local/python/bin/python3 /usr/local/bin/python [user@localhost Python-3.4.7]$ sudo ln -s /usr/local/python/bin/pip3.4 /usr/local/bin/pip [user@localhost ~]$ python --version Python 3.4.7 |
インストール後にpythonのバージョンを確認して一致していればOK。
サンプル集
Hello Worldその1
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#!/usr/local/python print("hello world") |
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[user@localhost basic]$ python hello1.py hello world |
Hello Worldその2
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#!/usr/local/python import sys sys.stdout.write("hello world\n") |
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[user@localhost basic]$ python hello2.py hello world |
printで改行しない
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#!/usr/local/python print("hello world", end="") |
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[user@localhost basic]$ python nokaigyo.py hello world[user@localhost basic]$ |
各種演算
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#!/usr/local/python print('2+1 =', 2+1) print('10-3 =', 10-3) print('7*4 =', 7*4) print('5/2 =', 5/2) print('5//2 =', 5//2) print('10%3 =', 10%3) print('2**10 =', 2**10) |
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[user@localhost basic]$ python ensan.py 2+1 = 3 10-3 = 7 7*4 = 28 5/2 = 2.5 5//2 = 2 10%3 = 1 2**10 = 1024 |
九九表
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#!/usr/local/bin/python for x in range(0,9): for y in range(0,9): print('{0}'.format('%2d ' % ((x+1) * (y+1))), end="") print('') |
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[user@localhost basic]$ python 99.py 1 2 3 4 5 6 7 8 9 2 4 6 8 10 12 14 16 18 3 6 9 12 15 18 21 24 27 4 8 12 16 20 24 28 32 36 5 10 15 20 25 30 35 40 45 6 12 18 24 30 36 42 48 54 7 14 21 28 35 42 49 56 63 8 16 24 32 40 48 56 64 72 9 18 27 36 45 54 63 72 81 |
円周率を求める
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#!/usr/local/bin/python import sys import math # # Machin's formula # π/4 = 4 * Arctan(1/5) - Arrctan(1/239) # def arctan(x, k): arctanx = 0 for n in range(0, k): arctanx += pow(-1, n) * (1/(2 * (n+1) - 1)) * pow(x, (2*(n+1) - 1)) return arctanx if __name__ == '__main__': argv = sys.argv if len(argv) != 2: print('usage : {0} <n>'.format(argv[0])) quit() for k in range(1, int(argv[1])): pi = 4 * (4 * arctan(1/5, k) - arctan(1/239, k)) print(pi) |
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[user@localhost basic]$ python pi.py 10 3.141592653589836 |
hexdumpコマンド風
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#!/usr/local/bin/python import sys if __name__ == '__main__': argv = sys.argv if len(argv) != 2: print('usage : {0} <file>'.format(argv[0])) quit() f = open(argv[1], 'rb') dat = f.read() for i in range(len(dat)): # 文字表示と改行 if (i >= 1 and i % 16 == 0): print('|', end=""); for n in range(16): if (0x20 <= int(dat[i+n-16]) and int(dat[i+n-16]) <= 0x7e): print('%c' % dat[i+n-16], end="") else: print('.', end="") print('|'); # オフセット表示 if (i == 0 or i % 16 == 0): print('%08x ' % i, end='') # 16進数表示 print('%02x ' % dat[i], end='') # 8byteで空白区切り if (i >= 1 and (i+1) % 8 == 0): print(' ', end="") # 最後に改行 print('') f.close |
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[user@localhost basic]$ hexdump -C Windows_Error.wav |head 00000000 52 49 46 46 24 9e 02 00 57 41 56 45 66 6d 74 20 |RIFF$...WAVEfmt | 00000010 10 00 00 00 01 00 02 00 44 ac 00 00 10 b1 02 00 |........D.......| 00000020 04 00 10 00 64 61 74 61 00 9e 02 00 00 00 00 00 |....data........| 00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| [user@localhost basic]$ python file.py Windows_Error.wav > test.txt [user@localhost basic]$ head test.txt 00000000 52 49 46 46 24 9e 02 00 57 41 56 45 66 6d 74 20 |RIFF$...WAVEfmt | 00000010 10 00 00 00 01 00 02 00 44 ac 00 00 10 b1 02 00 |........D.......| 00000020 04 00 10 00 64 61 74 61 00 9e 02 00 00 00 00 00 |....data........| 00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| |
Unixドメインソケット
サーバ側
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#!/usr/local/bin/python import os import sys import socket class UnixDomainServer: def __init__(self, socket_path): self.socket_path = socket_path def start(self): s = self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) s.bind(self.socket_path) s.listen(1) try: while True: sys.stdout.write("wait connection\n") connection, address = s.accept() sys.stdout.write("connected\n") self.accepted(connection, address) sys.stdout.write("disconnect\n") finally: os.remove(self.socket_path) def accepted(self, connection, address): data = connection.recv(1024) sys.stdout.write("receive from client: {}\n".format(data.decode())) if __name__ == '__main__': server = UnixDomainServer('./ud.sock') server.start() |
クライアント側
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#!/usr/local/bin/python import sys import socket class UnixDomainClient: def __init__(self, socket_path): self.socket_path = socket_path def start(self): s = self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) s.connect(self.socket_path) def send(self): message = "Hello" sys.stdout.write("send message to server : {0}\n".format(message)) self.socket.send(message.encode()) def close(self): self.socket.close() if __name__ == '__main__': client = UnixDomainClient('./ud.sock') client.start() client.send() client.close() |
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[user@localhost basic]$ python unix_sever.py wait connection connected receive from client: Hello disconnect wait connection [user@localhost basic]$ python unix_client.py send message to server : Hello |
今は全くまとまりが無いですが、サンプルが増えたら整理できればと思います。
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