325 lines
8.1 KiB
Plaintext
325 lines
8.1 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Reading data interactively"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"cat hello.py\n",
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"#!/usr/bin/env python3\n",
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"\n",
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"name = input(\"Please enter your name: \")\n",
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"print(\"Hello, \" + name)\n",
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"\n",
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"# ./hello.py \n",
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"# Please enter your name: Roger\n",
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"# #Output will be Hello, Roger"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"# defining a function called 'to_seconds' which takes hours, minutes and seconds as\n",
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"# inputs and returns their total equivalent in seconds by multiplying each with its\n",
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"# corresponding factor (3600 for hours, 60 for minutes) and then summing them up.\n",
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"def to_seconds(hours, minutes, seconds):\n",
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" return hours*3600+minutes*60+seconds\n",
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"\n",
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"# Print a welcome message to the user\n",
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"print(\"Welcome to this time converter\")\n",
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"\n",
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"# set 'cont' variable to \"y\" initially for entering into while loop.\n",
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"cont = \"y\"\n",
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"\n",
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"# while condition is true (user wants to continue), keep asking the\n",
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"# number of hours, minutes and seconds from the user and print their total equivalent\n",
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"# in seconds by calling 'to_seconds' function. Ask if they want to do another conversion.\n",
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"# If not, break the loop.\n",
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"while(cont.lower() == \"y\"):\n",
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" hours = int(input(\"Enter the number of hours: \"))\n",
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" minutes = int(input(\"Enter the number of minutes: \"))\n",
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" seconds = int(input(\"Enter the number of seconds: \"))\n",
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"\n",
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" print(\"That's {} seconds\".format(to_seconds(hours, minutes, seconds)))\n",
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" print()\n",
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" cont = input(\"Do you want to do another conversion? [y to continue] \")\n",
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" \n",
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"# print a goodbye message when user decides to stop the program.\n",
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"print(\"Goodbye!\")\n"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Standard streams\n",
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"I/O Streams"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"cat streams.py\n",
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"#!/usr/bin/env python3\n",
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"\n",
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"data = input(\"This will come from STDIN: \")\n",
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"print(\"Now we write it to STDOUT: \" + data)\n",
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"print(\"Now we generate an error to STDERR: \" + data + 1)\n",
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"\n",
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"./streams.py \n",
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"This will come from STDIN: Python Rocks!\n",
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"Now we write it to STDOUT: Python Rocks!\n",
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"\n",
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"cat greeting.txt \n",
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"Well hello there, STDOUT\n",
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"\n",
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"cat greeting.txt \n",
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"Well hello there, STDOUT\n",
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"\n",
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"ls -z"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Environment variables"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"HOME: /config\n",
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"SHELL: \n",
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"FRUIT: \n"
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]
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}
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],
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"source": [
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"# echo $PATH\n",
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"# /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\n",
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"# cat variables.py\n",
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"#!/usr/bin/env python3\n",
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"import os\n",
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"print(\"HOME: \" + os.environ.get(\"HOME\", \"\"))\n",
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"print(\"SHELL: \" + os.environ.get(\"SHELL\", \"\"))\n",
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"print(\"FRUIT: \" + os.environ.get(\"FRUIT\", \"\"))\n",
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"# ./variables.py\n",
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"# export FRUIT=Pineapple\n",
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"# ./variables.py"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Command-Line Arguments and Exit Status"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"cat parameters.py \n",
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"#!/usr/bin/env python3\n",
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"import sys\n",
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"print(sys.argv)\n",
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"\n",
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"./parameters.py\n",
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"['./parameters.py'] \n",
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"\n",
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"./parameters.py one two three\n",
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"['./parameters.py', 'one', 'two', 'three']\n",
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"\n",
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"\n",
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"wc variables.py\n",
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"7 19 174 variables.py \t\n",
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"echo $?\n",
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"0\n",
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"\n",
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"wc notpresent.sh\n",
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"wc: notpresent.sh: No such file or directory\n",
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"echo $?\n",
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"1\n",
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"\n",
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"#!/usr/bin/env python3\n",
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"\n",
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"import os\n",
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"import sys\n",
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"\n",
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"filename = sys.argv[1]\n",
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"\n",
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"if not os.path.exists(filename):\n",
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" with open(filename, \"w\") as f:\n",
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" f.write(\"New file created\\n\")\n",
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"else:\n",
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" print(\"Error, the file {} already exists!\".format(filename))\n",
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" sys.exit(1)\n",
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"\n",
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"./create_file.py example\n",
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"echo $?\n",
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"0\n",
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"\n",
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"cat example \n",
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"New file created\n",
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"./create_file.py example\n",
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"Error, the file example already exists!\n",
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"echo $?\n",
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"1"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"Python 2 and Python 3 handle input and raw_input differently.\n",
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"\n",
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"In Python 2\n",
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"\n",
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"- input(x) is roughly the same as eval(raw_input(x))\n",
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"- raw_input() is preferred, unless the author wants to support evaluating string expressions.\n",
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"- eval() is used to evaluate string expressions."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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">>> my_number = input('Please Enter a Number: \\n')\n",
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"Please Enter a Number: \n",
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"123 + 1\n",
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">>> print(my_number)\n",
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"123 + 1\n",
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">>> type(my_number)\n",
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"<class 'str'>\n",
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"\n",
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"\n",
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">>> my_number = input('Please Enter a Number: \\n')\n",
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"Please Enter a Number: \n",
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"123 + 1\n",
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">>> print(my_number)\n",
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"123 + 1\n",
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">>> eval(my_number)\n",
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"124"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Subprocesses"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Running system commands in Python"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"import subprocess\n",
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"subprocess.run([\"date\"])\n",
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"subprocess.run([\"sleep\", \"2\"])\n",
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"result = subprocess.run([\"ls\", \"this_file_does_not_exist\"])\n",
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"print(result.returncode)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Obtaining the output of a system command"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"result = subprocess.run([\"host\", \"8.8.8.8\"], capture_output=True)\n",
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"\n",
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"result = subprocess.run([\"host\", \"8.8.8.8\"], capture_output=True)\n",
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"print(result.returncode)\n",
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"\n",
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"result = subprocess.run([\"host\", \"8.8.8.8\"], capture_output=True)\n",
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"print(result.stdout)\n",
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"\n",
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"result = subprocess.run([\"host\", \"8.8.8.8\"], capture_output=True)\n",
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"print(result.stdout.decode().split())"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"import subprocess\n",
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"result = subprocess.run([\"rm\", \"does_not_exist\"], capture_output=True)\n",
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"\n",
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"import subprocess\n",
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"result = subprocess.run([\"rm\", \"does_not_exist\"], capture_output=True)\n",
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"print(result.returncode)\n",
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"\n",
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"import subprocess\n",
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"result = subprocess.run([\"rm\", \"does_not_exist\"], capture_output=True)\n",
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"print(result.returncode)\n",
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"print(result.stdout)\n",
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"print(result.stderr)"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.12.3"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 2
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}
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