02-data-types.ipynb

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   "source": [
    "# Data Types and Type Conversion"
   ]
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    "## Every value has a type.\n",
    "\n",
    "- Every value in a program has a specific _type_.\n",
    "- Integer (`int`): represents positive or negative whole numbers like 3 or -512.\n",
    "- Floating point number (`float`): represents real numbers like 3.14159 or -2.5.\n",
    "- Character string (usually called “string”, `str`): text.\n",
    "  - Written in either single quotes or double quotes (as long as they match).\n",
    "  - The quote marks aren’t printed when the string is displayed."
   ]
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   "source": [
    "## Use the built-in function `type` to find the type of a value.\n",
    "\n",
    "- Use the built-in function `type` to find out what type a value has.\n",
    "- Works on variables as well.\n",
    "  - But remember: the _value_ has the type — the _variable_ is just a label."
   ]
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   "source": [
    "print(type(52))"
   ]
  },
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   "source": [
    "fitness = 'average'\n",
    "print(type(fitness))"
   ]
  },
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   "metadata": {},
   "source": [
    "## Types control what operations (or methods) can be performed on a given value."
   ]
  },
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   "source": [
    "print(5 - 3)"
   ]
  },
  {
   "cell_type": "code",
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   "source": [
    "print('hello' - 'h')"
   ]
  },
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   "source": [
    "## You can use the `+` and `*` operators on strings.\n",
    "\n",
    "\"Adding\" character strings concatenates them."
   ]
  },
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   "source": [
    "full_name = 'Ahmed' + ' ' + 'Walsh'\n",
    "print(full_name)"
   ]
  },
  {
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   "id": "071bfb44-e9a4-4712-b576-7e56dd1f6302",
   "metadata": {},
   "source": [
    "Multiplying a character string by an integer _N_ creates a new string that consists of that character string repeated _N_ times."
   ]
  },
  {
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   "source": [
    "separator = '=' * 10\n",
    "print(separator)"
   ]
  },
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   "source": [
    "## Numbers don't have a length."
   ]
  },
  {
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   "outputs": [],
   "source": [
    "print(len(52))"
   ]
  },
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   "metadata": {},
   "source": [
    "## You can convert values to make them interoperable."
   ]
  },
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   "outputs": [],
   "source": [
    "print(1 + '2')"
   ]
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    "- Not allowed because it’s ambiguous: should `1 + '2'` be `3` or `'12'`?\n",
    "- Some types can be converted to other types by using the type name as a function."
   ]
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   "source": [
    "print(1 + int('2'))\n",
    "print(str(1) + '2')"
   ]
  },
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   "source": [
    "## Can mix integers and floats freely in operations.\n",
    "\n",
    "Integers and floating-point numbers can be mixed in arithmetic. Python 3 automatically converts integers to floats as needed."
   ]
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   "source": [
    "print('half is', 1 / 2.0)\n",
    "print('three squared is', 3.0 ** 2)"
   ]
  },
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   "source": [
    "## Variables only change value when something is assigned to them.\n",
    "\n",
    "If we make one cell in a spreadsheet depend on another, and update the latter, the former updates automatically.\n",
    "This does **not** happen in programming languages."
   ]
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   "source": [
    "variable_one = 1\n",
    "variable_two = 5 * variable_one\n",
    "variable_one = 2\n",
    "print('first is', variable_one, 'and second is', variable_two)"
   ]
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    "The computer reads the value of `variable_one` when doing the multiplication, creates a new value, and assigns it to `variable_two`.\n",
    "Afterwards, the value of `variable_two` is set to the new value and not dependent on `variable_one` so its value does not automatically change when `variable_one` changes."
   ]
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    "## Complex numbers.\n",
    "\n",
    "Python provides complex numbers, which are written as `1.0+2.0j`. If `val` is a complex number, its real and imaginary parts can be accessed using _dot notation_ as `val.real` and `val.imag`."
   ]
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   "source": [
    "a_complex_number = 6 + 2j\n",
    "print(a_complex_number.real)\n",
    "print(a_complex_number.imag)"
   ]
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    "## Key Points\n",
    "\n",
    "- **Every value has a type.**\n",
    "- **Use the built-in function `type` to find the type of a value.**\n",
    "- **Types control what operations can be done on values.**\n",
    "- **Strings can be added and multiplied.**\n",
    "- **Strings have a length (but numbers don’t).**\n",
    "- **Must convert numbers to strings or vice versa when operating on them.**\n",
    "- **Can mix integers and floats freely in operations.**\n",
    "- **Variables only change value when something is assigned to them.**"
   ]
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