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    "# A - Variables and operators\n",
    "\n",
    "![lec-0A-ga](lec-0A-ga.png)\n",
    "\n",
    "* To try it on *python tutor live*, [click here][preloaded ptl A]\n",
    "\n",
    "[preloaded ptl A]: http://www.pythontutor.com/live.html#code=%23%20%3D%3D%3D%20Lecture%20zero,%20part%20A%20%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%0A%23%20---%20Assignments%20-------------------------------------------------------------------------------------------------------------------------------------------------------------%0AR%20%3D%208.314%20%23%20Read%20as%20%22%20The%20value%20%228.314%22%20is%20assigned%20(%3D%29%20to%20the%20variable%20%22R%22.%20%22%0A%23%20---%20print%20-------------------------------------------------------------------------------------------------------------------------------------------------------------%0Aprint(R%29%20%23%20print%20the%20value%20assigned%20to%20R%0AT%20%3D%20273%0AP%20%3D%201e5%20%23%201e5%20means%201%20x%2010%5E5%0A%23%20---%20Operators%20-------------------------------------------------------------------------------------------------------------------------------------------------------------%0AV%20%3D%20R%20*%20T%20/%20P%20%23%20%22*%22%20means%20multiplication,%20%22/%22%20means%20division%0Aprint(T,P,V%29%20%23%20print%20the%20values%20assigned%20to%20T,%20P%20and%20V%20(%20separate%20each%20object%20with%20commas%20%29%0A%23%20%3D%3D%3D%20Notes%20%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%3D%0A%23%20---%20re%20assignment%20----------------------------------------------------------------------------------------------------------------------------------------------------------------%0AT%20%3D%20298%20%23%20assigns%20the%20new%20value%20%22298%22%20to%20the%20variable%20%22T%22%0Aprint(T,P,V%29%20%23%20V%20does%20not%20change,%20the%20calculation%20we%20performed%20before%20was%20a%20one%20time%20assignment,%20not%20a%20function%0AV%20%3D%20R%20*%20T%20/%20P%20%23%20perform%20the%20calculation%20again%0Aprint(T,P,V%29%20%23%20now%20V%20did%20change%0A%23%20---%20case%20sensibility%20--------------------------------------------------------------------------------------------------------------------------------------------------------%0At%20%3D%20373%20%23%20small%20t%20is%20a%20new%20independent%20variable%0Aprint(t,T%29%20%23case%20sensibility%20makes%20t%20and%20T%20two%20different%20variables%0A%23%20---%20memory%20independence%20--------------------------------------------------------------------------------------------------------------------------------------------------------%0AT1%20%3D%20273%20%23%20assign%20the%20value%20273%20to%20T1%0AT2%20%3D%20T1%20%23%20assign%20the%20value%20of%20T1%20to%20T2%0Aprint(T1,T2%29%20%23%20the%20value%20assigned%20to%20both%20of%20them%20is%20273%0AT2%20%2B%3D%2025%20%23%20increment%20the%20value%20of%20T2%20by%2025%0Aprint(T1,T2%29%20%23%20the%20value%20assigned%20to%20T1%20is%20still%20273,%20the%20value%20assigned%20to%20T2%20is%20273%20%2B%2025,%20therefore%20298&cumulative=false&curInstr=0&heapPrimitives=false&mode=display&origin=opt-live.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false"
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      "8.314\n",
      "273 100000.0 0.02269722\n",
      "298 100000.0 0.02269722\n",
      "298 100000.0 0.02477572\n",
      "373 298\n",
      "273 273\n",
      "273 298\n"
     ]
    }
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   "source": [
    "# The following code should be studied on the platform provided by http://www.pythontutor.com/live.html#mode=edit\n",
    "# This platform graphically depicts the behavior of variables, assignments, functions and pointers,\n",
    "# which is the major source of confusion among beginners in programming\n",
    "\n",
    "# === Lecture zero, part A ========================================================================================================================================================================\n",
    "\n",
    "# --- Assignments -------------------------------------------------------------------------------------------------------------------------------------------------------------\n",
    "\n",
    "R = 8.314\n",
    "\n",
    "# Read as \" The value \"8.314\" is assigned (=) to the variable \"R\". \"\n",
    "\n",
    "# Note the 'global frame' table\n",
    "\n",
    "# --- print -------------------------------------------------------------------------------------------------------------------------------------------------------------\n",
    "\n",
    "# print the value assigned to R\n",
    "\n",
    "print(R)\n",
    "\n",
    "# Note the 'print output' field\n",
    "\n",
    "T = 273\n",
    "# Note a new line on the 'global frame' table\n",
    "\n",
    "P = 1e5 # 1e5 means 1 x 10^5\n",
    "# Note a new line on the 'global frame' table\n",
    "\n",
    "# assignment to the result of an operation\n",
    "\n",
    "# --- Operators -------------------------------------------------------------------------------------------------------------------------------------------------------------\n",
    "\n",
    "V = R * T / P # \"*\" means multiplication, \"/\" means division\n",
    "# Note a new line on the 'global frame' table\n",
    "\n",
    "# print the values assigned to T, P and V ( separate each object with commas )\n",
    "print(T,P,V)\n",
    "# Note the 'print output' field\n",
    "\n",
    "# === Notes ========================================================================================================================================================================\n",
    "\n",
    "# --- re assignment ----------------------------------------------------------------------------------------------------------------------------------------------------------------\n",
    "\n",
    "# assigns the new value \"298\" to the variable \"T\" \n",
    "\n",
    "T = 298\n",
    "# Note the value on the second column in the line on the 'global frame' table corresponding to the variable T now changes \n",
    "\n",
    "print(T,P,V) # V does not change, the calculation we performed before was a one time assignment, not a function\n",
    "# Note the 'print output' field\n",
    "\n",
    "V = R * T / P # perform the calculation again\n",
    "\n",
    "print(T,P,V) # now V did change\n",
    "# Note the 'print output' field\n",
    "\n",
    "# we can automate that with functions -- see Lecture zero, part B\n",
    "\n",
    "# --- case sensibility --------------------------------------------------------------------------------------------------------------------------------------------------------\n",
    "\n",
    "t = 373 # small t is a new independent variable\n",
    "# Note a new line on the 'global frame' table\n",
    "\n",
    "print(t,T) #case sensibility makes t and T two different variables\n",
    "# Note the 'print output' field\n",
    "\n",
    "# --- memory independence --------------------------------------------------------------------------------------------------------------------------------------------------------\n",
    "\n",
    "# say\n",
    "T1 = 273 # assign the value 273 to T1\n",
    "T2 = T1 # assign the value of T1 to T2\n",
    "print(T1,T2) # the value assigned to both of them is 273\n",
    "\n",
    "T2 += 25 # increment the value of T2 by 25\n",
    "print(T1,T2) # the value assigned to T1 is still 273, the value assigned to T2 is 273 + 25, therefore 298\n"
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