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Вы можете ознакомиться и скачать презентацию на тему Basic programming. Доклад-сообщение содержит 74 слайдов. Презентации для любого класса можно скачать бесплатно. Если материал и наш сайт презентаций Mypresentation Вам понравились – поделитесь им с друзьями с помощью социальных кнопок и добавьте в закладки в своем браузере.

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Tirgul 2 Basic programming

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Overview Variables Types : int, float, string User input Functions with input and output The Boolean type and Boolean operations Conditional operation (if…else…)

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Variables - Motivation Write a program which calculates the difference in the areas of a square with side = 1.5 and the circle enclosed within it.

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Variables - Motivation 1.5*1.5 –3.14*(1.5/2 )**2

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Variables - Motivation Two problems : The expression 1.5*1.5 –3.14*(1.5/2 )**2 is really difficult to understand : When you get back to it after one week When debugging When the side of the square changes. Should you have an expression per side-length? Side=1.5 : 1.5*1.5 – 3.14*(1.5/2 )**2 Side=3.7 : 3.7*3.7 – 3.14*(3.7/2 )**2 Side=9 : 9*9 – 3.14*(9/2) )**2

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Variables - Motivation Wouldn’t it be much more readable, modular, easy to modify in this format : side = 1.5, PI = 3.14 square_area = side*side radius = side/2 circle_area = PI*r2 answer = square_area – circle_area

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Variables Variables let us define “memory units” which can “remember” values. Variables have 2 main components : name value

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Variables Variables have 2 main functionalities : Set their value number_of_apples = 3 Get their values tomorrow_apples = number_of_apples + 1

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Variables – Naming conventions Use lower case letter number,apples Separate multiple words with underscore word_and_more_words Use meaningful names for names (don’t be shy to open a dictionary) z = x/y ??? words_per_page = words_in_book/number_of_pages  Use capitals for constants (variables which do not change their value after first initialization) PI = 3.14, ERROR_MESSAGE = ‘You had an error’

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Types Can we perform the following command ? x = 3 + 5 And this one ? x = 3 + “hello” Why not? 3 and ‘hello’ are not of the same category. The name Python gives to the categories which differentiate between objects such as 3 and ‘hello’ are called type.

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$Types int (Integer) : represent an Integer number (מספר שלם). E.g. 1024, 13, 92,0 float : represent a fractional number. E.g. : 0.0, 15.62545, 3.14...$

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Types int (Integer) : represent an Integer number (מספר שלם). E.g. 1024, 13, 92,0 float : represent a fractional number. E.g. : 0.0, 15.62545, 3.14 str (String) : represent text, a list of characters. Defined between a couple of apostrophe or quotes (equivalent). E.g. ‘hello’, “hello”, ‘13’

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Types The type() function receives a value and return its type. type(3)  int type(3.0)  float type('3.0')  str What happens when we mix types? type(1 + 0.5)  float type(1 + 'some string')  ?

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Types What happens when we mix types? type(1 + 'some string') TypeError: unsupported operand type(s) for +: 'int' and 'str' This is an error message which tells us we have tried to execute a command not supported by the language.

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Error message Error messages are our friends, they help us detect bugs in our program and point out how to fix them. When you get an error “keep calm and read the error message”.

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Error message - Example >>> x = 49 >>> x/(49**0.5 - 7) Traceback (most recent call last): File "C:/my_python/test.py", line 9, in x/(49**0.5 - 7) ZeroDivisionError: float division by zero Remember - “keep calm and read the error message”