Intro Python Y9

​The following are examples of ACCEPTABLE variable names:

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• ​apples, car, costs

• b8, a12, z1000

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​The following are example of NOT ACCEPTABLE variable names:

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• ​1, 100, 3000, 22, 14 (a variable can not start with a number)

• ​print, input, def (these are keywords used within python)

​Part of a program that can be assigned a specific value

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• ​Made up of two parts; an identifier, and a value.

• ​This value CAN change while the program is running.

​Part of a program that can be assigned a specific value

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• ​Made up of two parts; an identifier and a value.

• ​This value can NOT change while the program is running.

​It's important to comment your code often.

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​When commenting code, use the symbol # followed by your comment

​Variable names are limited to certain characters when they are defined in your code. Using incorrect Variable names will result in your code displaying the error:

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​"Syntax Error: invalid syntax"

All data in Python is represented by 'objects' or the relationship between 'objects'.

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​Every object has three things:

• ​An 'identity'

• ​A 'type'

• ​A 'Value'

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​An objects 'identity' never changes once it has been created - it is forever saved in the Python's memory.

An object's type determines what operations that it supports, for example:

• ​Does it have a length? which then defines the possible values for objects of that type.

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​The type() function returns an object's type (which is an object itself)

​Just like an object's 'identity', an object's type is also unchangeable.

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The values of some objects can change though...

​There are several built-in functions that let you convert one data type into another. These functions return a new object representing the converted value, such as:

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• ​int(x) which converts x into an integer

• ​float(x) which converts x into a floating-point number

• ​str(x) which converts x into a string representation