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Here are the rules that you have to follow for defining the python where.

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The first one is a variable must start with a letter or the underscored character.

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So names like Python is valid.

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Also name like underscored.

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Python is also one next a variable name can start with a number.

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So you can have a variable name that starts with the seven python but you can have a variable name which

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is something like this python 0 0 or 1.

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This is valid.

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So the next one is a variable name can only contain alphanumeric characters and underscored.

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Next is variable names.

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Case into 2 Say for example.

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Each in which all of the letters in lowercase and each year with the latest.

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It is incompetent and age the rateable age your which is all letters in uppercase are different variables

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then assigning a variable name to a value.

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There are certain it is a code word in Python that we should not use as variable names because these

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words already have special meaning in Python.

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Say for example the dissolved word if this is used this the if keyword is used in if clause or the if

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statement or it is old word for it.

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True and so on these exact words cannot be used as variable names.

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And if you try to assign a value to any of these reserved words or key words python will raise and edit

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so let's see this.

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In the Jupiter known book say for example we are going to use the resource to keyword forward as a variable

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name and assign the value to.

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And when you execute this line you get this error a syntax error and in order to see the list of desired

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keywords you can use the help function and then parse the argument.

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Key word and this will give you the list of keywords in Python.

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And these should not be used as variable names in your python programs

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similarly.

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There are several built in functions which are included in the python standard library and we should

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not use the names of these functions as variable names.

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Otherwise the reference to the built in function will be lost in order to understand this.

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Let's define a variable X assign the value to we use the built in function i.e. in order to know the

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memory address where the variable is pointing to.

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So we'll call the built in function idea and pass the variable x to this function.

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And this is the memory address.

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To which the variable x is pointing to.

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Now I'm going to use the built in function D as a variable name in my program and say I'm going to assign

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the value numeric value 5

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so I.D. is now pointing to value 5.

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Now if I call these same built in function and pass the variable x to this function I'm going to get

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a runtime error.

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So we should not use the names of these functions as variable names in other programs.

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Because overwriting a built in function might have undesired side effects

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similarly we should not be using built in functions like I n d for integer flawed as these are for string

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list type I.D. and so on as variable names in other programs.