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"<small><small><i>\n",
"All the IPython Notebooks in **Python Flow Control Statements** lecture series by Dr. Milaan Parmar are available @ **[GitHub](https://github.com/milaan9/03_Python_Flow_Control)**\n",
"</i></small></small>"
]
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"# Python `if-elif-else` statement\n",
"\n",
"So far, we have presented a Boolean option for conditional statements, with each **[if statement](https://github.com/milaan9/03_Python_Flow_Control/blob/main/001_Python_if_statement.ipynb)** evaluating to either **`True`** or **`False`**. In Python, the **`if-elif-else`** condition statement has an **`elif`** keyword used to chain multiple conditions one after another."
]
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"### Syntax:\n",
"\n",
"```python\n",
"if condition-1: \n",
" statement 1 \n",
"elif condition-2:\n",
" stetement 2 \n",
"elif condition-3:\n",
" stetement 3 \n",
" ... \n",
"else: \n",
" statement \n",
"```\n",
"\n",
"1. The **`elif`** is short for else if. It allows us to check for multiple expressions.\n",
"\n",
"2. If the condition for **`if`** is **`False`**, it checks the condition of the next **`elif`** block and so on.\n",
"\n",
"3. If all the conditions are **`False`**, the body of **`else`** is executed.\n",
"\n",
"4. Only one block among the several **`if-elif-else`** blocks is executed according to the condition.\n",
"\n",
"5. The **`if`** block can have only one **`else`** block. But it can have multiple **`elif`** blocks.\n",
"\n",
"<div>\n",
"<img src=\"img/eif0.png\" width=\"500\"/>\n",
"</div>"
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"Zero\n"
]
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"source": [
"# Example 1:\n",
"\n",
"'''In this program, we check if the number is positive or negative or zero and \n",
"display an appropriate message'''\n",
"\n",
"num = 0\n",
"\n",
"# Try these two variations as well:\n",
"# num = 0\n",
"# num = -4.5\n",
"\n",
"if num > 0:\n",
" print(\"Positive number\")\n",
"elif num == 0:\n",
" print(\"Zero\")\n",
"else:\n",
" print(\"Negative number\")"
]
},
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"metadata": {},
"source": [
"**Explanation:**\n",
"\n",
"When variable **`num`** is positive, **`Positive number`** is printed.\n",
"\n",
"If **`num`** is equal to 0, **`Zero`** is printed.\n",
"\n",
"If **`num`** is negative, **`Negative number`** is printed. "
]
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"name": "stdout",
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"text": [
"num1 is equal to num2\n"
]
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"source": [
"# Example 2:\n",
"\n",
"num1, num2 = 5, 5\n",
"if(num1 > num2):\n",
" print(\"num1 is greater than num2\")\n",
"elif(num1 == num2):\n",
" print(\"num1 is equal to num2\")\n",
"else:\n",
" print(\"num1 is less than num2\")"
]
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"name": "stdout",
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"text": [
"x<y\n"
]
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"source": [
"# Example 3:\n",
"\n",
"x = 10\n",
"y = 12\n",
"if x > y:\n",
" print(\"x>y\")\n",
"elif x < y:\n",
" print(\"x<y\")\n",
"else:\n",
" print(\"x=y\")"
]
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"text": [
"A grade\n"
]
}
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"source": [
"# Example 4:\n",
"\n",
"grade = 96\n",
"\n",
"if grade >= 90:\n",
" print(\"A grade\")\n",
"elif grade >=80:\n",
" print(\"B grade\")\n",
"elif grade >=70:\n",
" print(\"C grade\")\n",
"elif grade >= 65:\n",
" print(\"D grade\")\n",
"else:\n",
" print(\"Failing grade\")"
]
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"text": [
"Admin\n",
"Editor\n",
"Guest\n",
"Wrong entry\n"
]
}
],
"source": [
"# Example 5:\n",
"\n",
"def user_check(choice):\n",
" if choice == 1:\n",
" print(\"Admin\")\n",
" elif choice == 2:\n",
" print(\"Editor\")\n",
" elif choice == 3:\n",
" print(\"Guest\")\n",
" else:\n",
" print(\"Wrong entry\")\n",
"\n",
"user_check(1) # Admin\n",
"user_check(2) # Editor\n",
"user_check(3) # Guest\n",
"user_check(4) # Wrong entry"
]
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"cell_type": "markdown",
"metadata": {},
"source": [
"## if-elif-else statements with logical operators\n",
"\n",
"We can avoid writing nested condition by using logical operator **`and`**."
]
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"metadata": {},
"source": [
"### if-elif-else statements `and` Logical Operator\n",
"\n",
"**Syntax:**\n",
"\n",
"```py\n",
"if condition and condition:\n",
" code\n",
"```"
]
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"name": "stdout",
"output_type": "stream",
"text": [
"A is zero\n"
]
}
],
"source": [
"a = 0\n",
"if a > 0 and a % 2 == 0:\n",
" print('A is an even and positive integer')\n",
"elif a > 0 and a % 2 != 0:\n",
" print('A is a positive integer')\n",
"elif a == 0:\n",
" print('A is zero')\n",
"else:\n",
" print('A is negative')"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### if-elif-else statements `or` Logical Operator\n",
"\n",
"**Syntax:**\n",
"\n",
"```py\n",
"if condition or condition:\n",
" code\n",
"```"
]
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"name": "stdout",
"output_type": "stream",
"text": [
"Access denied!\n"
]
}
],
"source": [
"user = 'Arthur'\n",
"access_level = 3\n",
"if user == 'admin' or access_level >= 4:\n",
" print('Access granted!')\n",
"else:\n",
" print('Access denied!')"
]
},
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"metadata": {},
"source": [
"## 💻 Exercises ➞ <span class='label label-default'>List</span>\n",
"\n",
"### Exercises âžž <span class='label label-default'>Level 1</span>\n",
"\n",
"1. Get two numbers from the user using input prompt. If **`num_1`** is greater than **`num_2`** return **`num_1`** is greater than **`num_2`**, if **`num_1`** is less **`num_2`** return **`num_1`** is smaller than **`num_2`**, else **`num_1`** is equal to **`num_2`**. Output:\n",
"\n",
"```sh\n",
"Enter number one: 9\n",
"Enter number two: 6\n",
"9 is greater than 6\n",
"```\n",
"\n",
"### Exercises âžž <span class='label label-default'>Level 2</span>\n",
"\n",
"1. Write a code which gives grade to students according to theirs scores:\n",
" \n",
"```py\n",
" 80-100, A\n",
" 70-89, B\n",
" 60-69, C\n",
" 50-59, D\n",
" 0-49, F\n",
"```\n",
"\n",
"2. Check if the season is Autumn, Winter, Spring or Summer. \n",
" - If the user input is:\n",
" - September, October or November, the season is Autumn.\n",
" - December, January or February, the season is Winter.\n",
" - March, April or May, the season is Spring\n",
" - June, July or August, the season is Summer\n",
"\n",
"\n",
"3. The following list contains some fruits:\n",
" - If a fruit doesn't exist in the list add the fruit to the list and print the modified list. If the fruit exists print **`('That fruit already exist in the list')`** \n",
" \n",
"```py\n",
" fruits = ['banana', 'orange', 'mango', 'pear']\n",
"``` \n",
"\n",
"\n",
"### Exercises âžž <span class='label label-default'>Level 3</span>\n",
"\n",
" 1. Here we have a person dictionary. Feel free to modify it!\n",
" \n",
"```py\n",
" person={\n",
" 'first_name': 'Milaan',\n",
" 'last_name': 'Parmar',\n",
" 'age': 96,\n",
" 'country': 'Finland',\n",
" 'is_marred': True,\n",
" 'skills': ['Python', 'Matlab', 'R', 'C', 'C++'],\n",
" 'address': {\n",
" 'street': 'Space street',\n",
" 'zipcode': '02210'\n",
" }\n",
" }\n",
"```\n",
"\n",
" * Check if the person dictionary has skills key, if so print out the middle skill in the skills list.\n",
" * Check if the person dictionary has skills key, if so check if the person has 'Python' skill and print out the result.\n",
" * If a person skills has only Python and Matlab, print('He knows machine learning'), if the person skills has Python, and R print('He knows statistics'), if the person skills has C, and C++, Print('He knows software development'), else print('unknown title') - for more accurate results more conditions can be nested!\n",
" * If the person is married and if he lives in Finland, print the information in the following format:\n",
"\n",
"```py\n",
" Milaan Parmar lives in Finland. He is married.\n",
"```"
]
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