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ITP 313 Python Fundamentals and Data Types *rga/2022 Python Fundamentals ▪ Program structure ▪ Comments and Whitespace ▪ Statements and Expressions ▪ Variables ▪ Data Types ▪ Operators ▪ Math functions Python Fundamentals Program structure The complete classic “Hello World” progr...

ITP 313 Python Fundamentals and Data Types *rga/2022 Python Fundamentals ▪ Program structure ▪ Comments and Whitespace ▪ Statements and Expressions ▪ Variables ▪ Data Types ▪ Operators ▪ Math functions Python Fundamentals Program structure The complete classic “Hello World” program, Pythonic style. print(“Hello World!”) #That’s it! ▪ No header! ▪ No semi-colon! ▪ No braces! ▪ One line! ▪ Simple! Python Fundamentals Whitespace whitespace is meaningful in python: especially indentation and placement of newlines. Use a newline to end a line of code (press ENTER) Use \ when you must go to next line prematurely. No braces { } to mark blocks of code in python… use consistent indentation instead. The first line with less indentation is outside of the block. The first line with more indentation starts a nested block a colon (:) appears at the start of a new block. Python Fundamentals Comments Start comments with # – the rest of line is ignored. Can include a “documentation string” as the first line of any new function or class that you define. Def myFunction(x, y): “““this is the docstring. This function does blah blah blah.””” # The comment would go here...  Python Fundamentals Primitive Data Types int - The integer numbers (e.g. 2, 4, 20) Float - the ones with a fractional part (e.g. 5.0, 1.6) Complex In addition to int and float, Python supports other types of numbers, such as Decimal and Fraction. Python also has built-in support for complex numbers, and uses the j or J suffix to indicate the imaginary part (e.g. 3+5j).  Primitive Data Types STRING Besides numbers, Python can also manipulate strings, which can be expressed in several ways. They can be enclosed in single quotes ('...') or double quotes ("...") with the same result. \ can be used to escape quotes: >>> 'spam eggs' # single quotes 'spam eggs’. >>> 'doesn\'t' # use \' to escape the single quote... "doesn’t” >>> "doesn't" #...or use double quotes instead "doesn't" >>> '"Yes," he said.' ‘“Yes," he said.' >>> "\"Yes,\" he said.“ >>> '"Isn\'t," she said.' '"Yes," he said.‘ '"Isn\'t," she said.' Sample numeric values int long float complex 10 51924361L 0.0 3.14j 100 -0x19323L 15.20 45.j -786 0122L -21.9 9.322e-36j 080 0xDEFABCECBDAECBFBAEL 32.3+e18.876j -0490 535633629843L -90. -.6545+0J -0x260 -052318172735L -32.54e100 3e+26J 0x69 -4721885298529L 70.2-E12 4.53e-7j Type Casting In Python Sometimes in our program, it is necessary for us to convert from one data type to another, such as from an integer to a string. This is known as type casting. There are three built-in functions in Python that allow us to do type casting. These are the int(), float(), and str() functions. To change a float to an To change a string to an integer integer >>>int(5.712987) >>>int(“4”) 5 4 To change integer or string to float integer or a float to a string >>>float(2) >>>str(2.1) 2.0 ‘2.1’ >>>float(“2”) >>>str(2) 2.0 ‘2’ Python Fundamentals Math Functions some requires import math # Math Function & Returns ( Description ) 1 abs(x): The absolute value of x: the (positive) distance between x and zero. 2 ceil(x): The ceiling of x: the smallest integer not less than x. 3 exp(x): The exponential of x: e 4 floor(x): The floor of x: the largest integer not greater than x. 5 log(x): The natural logarithm of x, for x > 0. 6 log10(x): The base-10 logarithm of x for x > 0. 7 max(x1, x2,...): The largest of its arguments: the value closest to positive infinity 8 min(x1, x2,...): The smallest of its arguments: the value closest to negative infinity. 9 pow(x, y): The value of x**y. round(x [,n]): x rounded to n digits from the decimal point. Python rounds away 10 from zero as a tie-breaker: round(0.5) is 1.0 and round(-0.5) is -1.0. 11 sqrt(x): The square root of x for x > 0. Python Fundamentals Type casting Functions # Function & Description 1 int(x [,base]): Converts x to an integer. The base specifies if x is a string. 2 float(x): Converts x to a floating-point number. 3 complex(real [,imag]): Creates a complex number. 4 str(x): Converts object x to a string representation. 5 repr(x): Converts object x to an expression string. 6 eval(str): Evaluates a string and returns an object. 7 chr(x): Converts an integer to a character. 8 unichr(x): Converts an integer to a Unicode character. 9 ord(x): Converts a single character to its integer value. What are variables? Variables are names given to data that we need to store and manipulate in our programs. For instance, suppose your program needs to store the age of a user. To do that, we can name this data userAge and define the variable age using the following statement. age = 0 We can also define multiple variables at one go. To do that simply write userAge, userName = 30, ‘Peter’ Naming a Variable 1. A variable name in Python can only contain letters (a - z, A - Z), numbers or underscores (_). 2. First character cannot be a number. 3. Cannot use reserved words. 4. Variable names are case sensitive There are two conventions when naming a variable in Python. We can either use the Camel case notation or use underscores. 1. thisIsAVariableName 2. this_is_a_variable_name Python Fundamentals Variables follows same naming convention as C, C++, Java Primitive Data Types bool, int, long, float, complex, string Variable Declaration Data typing is implicit and automatic upon assignment a=0 integer b = 123L long integer x = 1.23 float s = “abc” string s = ‘abc’ string isEven = (n % 2 == 0) Boolean The Assignment Sign Note that the = sign in the statement userAge = 0 has a different meaning from the = sign we learned in Math. In programming, the = sign is known as an assignment sign. It means we are assigning the value on the right side of the = sign to the variable on the left. A good way to understand the statement userAge = 0 is to think of it as userAge 4 + spam*3 >>> '2' + 2 References: Python 3.7.4 Documentation – Python Tutorial Copyright Python and this documentation is: Copyright © 2001-2019 Python Software Foundation. All rights reserved. Copyright © 2000 BeOpen.com. All rights reserved. Copyright © 1995-2000 Corporation for National Research Initiatives. All rights reserved. Copyright © 1991-1995 Stichting Mathematisch Centrum. All rights reserved. © Copyright 2001-2019, Python Software Foundation