Revision as of 14:23, 1 November 2019

variables

variables can be integers, floats, or boolean. Integers are whole numbers, floats are numbers with remainders, boolean is either True of False.

variable=integer

float vars

If you want the fraction included in the var, you need to define it as a float, otherwise python will automatically round the result to a whole number.

 floating_var = float(7)/2

This will give you the fraction from dividing 7/2.

convert int to string

age = 13
print str(age)

convert string to int

n1 = "100"
n2 = "10"
int_addition = int(n1) + int(n2)

convert to float

n1 = "7.5"
print float(n1)

verify is alpha (letters) only

variable_name.isalpha()
ie.
if variable.isalpha():

arithmetic operators

add/subtract/multiply/divide/exponentiation/modulo

exponentiation (exponential, similar to square roots)

2 ** 3=8   (2*2*2)

modulo (remainder)

5 % 2=1  (5/2 = 2 with a remainder of 1)

shorthand

+= add vars and update first var
ie. sandwich_price += sales_tax

-= subtract vars and update first var
ie. money_in_wallet -= sandwich_price

comments

# for single like quote or """ quote """ for multi line quote

#quote
"""quote
quote"""

print

display output

print "Hello World"

display specific letter, left to right, 0 forward

print "TEST"[0] = "T"

strings

multi-line string

for strings that span multiple lines, use triple quotes

address_string = """136 Whowho Rd
Apt 7
Whosville, WZ 44494"""

string continuation

it appears you can continue a string by using \ though i've only seen this behavior using string concatenation

ie. 
print "Ah, so your name is %s, your quest is %s, " \
"and your favorite color is %s." % (name, quest, color)

string methods

len() ; lower() ; upper() ; str()

len() = get length of string - applies to anything within the parentheses

len(length)   =   6

lower() = convert to lowercase - applies to only the value after the "." . Dot notation only works on strings

LOWERCASE.lower()   =   lowercase

upper() = convert to uppercase - applies to only the value after the "." . Dot notation only works on strings

uppercase.upper()   =   UPPERCASE

str() = convert to string - applies to anything within the parentheses

str(3.14)   =   "3.14"

String Formatting

concatenating strings through short hand

string_1 = "Camelot"
string_2 = "place"
print "Let's not go to %s. 'Tis a silly %s." % (string_1, string_2)

define var length

when doing concatenating, you can specify the var length to be displayed. this is especially helpful with numbers when trying to apply formatting.

print '%02d:%02d:%02d' % (now.hour, now.minute, now.second)
21:02:18

notice how the minute is 02. If this was not defined to be (2) digits, it would have only been a 2 without the preceeding 0.

user input

by default, raw_input creates a variable defined as a string.

variable = raw_input("display message")

name=raw_input("display message")

If you want to define another type of variable, such as an int or float, you can wrap the raw_input function like so:

number = int(raw_input("Enter Number:"))

slice

parse certain characters from a variable

x=variable
 print x[1:3]
 ari
 
 x=variable
 print [3:len(x)]
 iable

Lists

Another data type, lists can be used to store a list of items.

ie. numbers = [5, 6, 7, 8]

Lists can also be empty.

numbers = []

Access by Index

You can access individual items, starting from 0.

ie. numbers = [5, 6, 7, 8]
print numbers[3]
>8

remove character special value

like with regular expression, you can remove a characters normal value by adding \ in front, however this does not work with all characters in python

'Help! Help! I\'m being repressed!'

Comparators

basic comparisons

==, !=, <, <=, >, or >=

Tuple

You can use a tuple as a way to compare against multiple values. I've only used it when doing an equal == comparison.

if type(num) in (int, float):
  return abs(num)

In other words, if the type of the num parameter is equal to either int or float, then return the absolute value against 0.

Boolean Operators

and, or, or not

true, false

True and True is True
True and False is False 
False and True is False
False and False is False

True or True is True
True or False is True
False or True is True
False or False is False

Not True is False
Not False is True

Conditional Statements

if, else, and elif.

def clinic():
   print "You've just entered the clinic!"
   print "Do you take the door on the left or the right?"
   answer = raw_input("Type left or right and hit 'Enter'.").lower()
   if answer == "left" or answer == "l":
       print "This is the Verbal Abuse Room, you heap of parrot droppings!"
   elif answer == "right" or answer == "r":
       print "Of course this is the Argument Room, I've told you that already!"
   else:
       print "You didn't pick left or right! Try again."
       clinic()

clinic()

datetime

builtin function within python with date time variable.

print

print datetime.now()

manipulate

print datetime.now().year
print datetime.now().month
print datetime.now().day

functions

functions are defined using def

ie. def my_function()

parameters

parameters can be passed into a function inline when it is called.

ie def my_function(var_a, var_b, var_c)

return

return returns the chosen value from the function, you can chose any value you want. Without return, the function will return None.

ie. def test_func(num):
  number = num * 1
  return number

print test_func(1)
>1

def test_func2(num):
  number = num * 1

print test_func2(1)
>None

Python baked in functions

max()

returns the largest number from X arguments

ie.
def biggest_number(*args):
  return max(args)

min()

opposite of max, gives the smallest number from X arguments

ie.
def smallest_number(*args):
  return min(args)

abs()

absolute value from 0.

ie.
print abs(5)
>5

type()

returns the type of data in the argument. (ie, is it an int or float or string, etc)

number_ = int(1)
float_ = float(4.5)
string_ = str("hello")

print type(number_)
print type(float_)
print type(string_)

Modules

import

you can import functions from modules to make reusing code easier. There are also built-in functions already in python to help save you time.

 import math
 math.sqrt(25)
> 5.0 

you can also import single functions to save you a bit of typing, albeit not much.

from module import function
ie. from math import sqrt

now you can call the function directly without having to put the module in front.

 sqrt()

or import all the functions

from module import *

List all functions from a module

import math
print dir(math)