Monday, July 21, 2014

My Mathematical Notes for Python (so far)

Official website:

Latest version: 3.4 (at the time of this blog entry)

My mathematical notes on Python so far:

This is from the 3.4 instructions but should hold in the 2.7 version as well. I am trying to find a good iOS app to do this.

* A good suggestion is to watch a few tutorial YouTube videos on Python. Onestopprogramming has a good set of tutorials. Python is capable of doing many things, including working with computer files, my focus will be on some of the mathematical capabilities of Python.

* The uses of the equals symbol ( = ) in Python:

(1) A single equal sign means assignment.
x = 4 stores "4" in the variable x.
str = "Eddie" or str = 'Eddie' stores "Eddie" in the variable str.

(2) Two equals signs mean comparison, does x equal y? ( x = y ?)
12==12 returns True

(3) An exclamation mark in front of an equals sign means the comparison, does x not equal y? ( x ≠ y ?)
12!=12 returns False

* Variables that are assigned are defaulted to strings. In order to use variables to represent numbers, we must first declare them as such. The declarations are:

int: integer
long: long integer
float: floating numbers
complex: complex numbers

Example: float(x) declares x as a floating variable.

* Working with floating numbers can bring "weird results" due to Python internally representing every number as a binary representation (0s and 1s). For example,

2.2 * 2 returns 4.40000000000000004

Although the PC version returns 4.4. So this may just be he iOS or a not so good app I was using a the time (Python 3.3 iOS app).

In order to get this answer in more acceptable form. This requires the format declaration. It's syntax is generally this:

"{:.xf}".format(answer, expression, variable, etc..)

Where x is the number of decimal places desired.

Back to our example, let's express 2.2 * 2 using four decimal places:

"{:.4f}".format(2.2*2) returns '4.4000'

* To access mathematical functions beyond arithmetic, we must first import the math library. This is done usually at the beginning of each script (program).

Syntax: import math

Common math functions are what you would expect:

math.ceil(x): ceiling
math.fabs(x): absolute value
math.factorial(x): factorial of x, integers only
math.gamma(x): the gamma function, Γ(x)
math.erf(x): error function
math.fsum(list): sum of a lists elements (in single square brackets)
math.exp(x): e^x
math.log(x, base): logarithm. Leave base out for natural logarithms ( ln x ).
math.pow(x, y): x^y. More expansive than using the double asterisk. ( x ** y )
math.sqrt(x): √x

math.sin(x), math.cos(x), math,tan(x): sine, cosine, and tangent, respectively. The angle is always in radians.
math.asin(x), math.acos(x), math.atan(x): arcsine, arccosine, and arctangent, respectively. The angle returned is in radians.
There are hyperbolic versions of these functions.

math.degrees(x): convert from radians to degrees
math.radians(x): convert from degrees to radians
math.pi: π
math.e: e

A complete list can be found in the python documentary.

* Quick math symbols that don't need the math library to be imported:

Arithmetic functions: +, -, *, and /. (For those new to programming, * represents × and / represents ÷)

Power: ** (two asterisks)

Modoluo: %

Representing exponential powers of 10: e+N or e-N

That is my quick notes for now. I want to post some programs using the Python language in the upcoming weeks.


1 comment:

  1. If you want your ex-girlfriend or ex-boyfriend to come crawling back to you on their knees (no matter why you broke up) you gotta watch this video
    right away...

    (VIDEO) Get your ex back with TEXT messages?


Fun with the Radio Shack EC-4026

Fun with the Radio Shack EC-4026   (Equivalent of the Casio fx-4500P) Programming Notes   The syntax for prompting ...