Python/Basic Code

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Line 1: Line 1:
 +
=reserved words=
 +
These are some words that you should not use in python as they are reserved.
 +
;list
 +
:reserved word that should not be used as a variable name.
 +
 
=variables=
 
=variables=
 
:variables can be integers, floats, or boolean.  Integers are whole numbers, floats are numbers with remainders, boolean is either True of False.
 
:variables can be integers, floats, or boolean.  Integers are whole numbers, floats are numbers with remainders, boolean is either True of False.
Line 43: Line 48:
 
==display specific letter, left to right, 0 forward==
 
==display specific letter, left to right, 0 forward==
 
  print "TEST"[0] = "T"
 
  print "TEST"[0] = "T"
 +
==trailing comma==
 +
adding a trailing comma ensures that we keep printing on the same line.
 +
<nowiki>print number,</nowiki>
 +
 
=strings=
 
=strings=
 
==multi-line string==
 
==multi-line string==
Line 90: Line 99:
 
  print [3:len(x)]
 
  print [3:len(x)]
 
  iable</nowiki>
 
  iable</nowiki>
 +
 +
slicing a string can be tricky too.  think about this example '''<code>[:3]</code>''', this says to slice characters 0 through 3 from the string, however it does not include 3.  the key to the logic is the word '''upto''', we are slicing from 0 upto 3.  In otherwords, if you think about it as a fraction, we slice from 0 to 2.9999..., so it would '''NOT''' be inclusive of the 3rd character.<br>
 +
this is also why if we do '''<code>[3:]</code>''' that would be '''from''', we are slicing from 3 to the end of the string, ie. 3+, so it would be inclusive of the 3rd character.
  
 
=Lists=
 
=Lists=
Line 110: Line 122:
 
> []</nowiki>
 
> []</nowiki>
 
I'm not sure why it behaves like this.
 
I'm not sure why it behaves like this.
 +
==removing==
 +
There are a few different ways to remove items from lists.
 +
===.pop()===
 +
returns the item being removed and then removes it from the list.
 +
<nowiki>n = [1, 3, 5]
 +
n.pop(1)
 +
# Returns 3 (the item at index 1)
 +
print n
 +
# prints [1, 5]</nowiki>
 +
===.remove()===
 +
removes the actual item if found
 +
<nowiki>n.remove(1)
 +
# Removes 1 from the list,
 +
# NOT the item at index 1
 +
print n
 +
# prints [3, 5]</nowiki>
 +
===del()===
 +
deletes the item at the given index
 +
<nowiki>del(n[1])
 +
# Doesn't return anything
 +
print n
 +
# prints [1, 5]</nowiki>
 +
 +
==Generating Examples==
 +
Generate a list of even numbers from 0-51
 +
<nowiki>evens_to_50 = [i for i in range(51) if i % 2 == 0]</nowiki>
 +
Double numbers
 +
<nowiki>doubles = [x * 2 for x in range(1, 6)]</nowiki>
  
 
=remove character special value=
 
=remove character special value=
Line 125: Line 165:
 
:and, or, or not
 
:and, or, or not
 
===true, false===
 
===true, false===
−
  True and True is True
+
  <nowiki>True and True is True
−
True and False is False  
+
True and False is False  
−
False and True is False
+
False and True is False
−
False and False is False
+
False and False is False
 
   
 
   
−
True or True is True
+
True or True is True
−
True or False is True
+
True or False is True
−
False or True is True
+
False or True is True
−
False or False is False
+
False or False is False
 
   
 
   
−
Not True is False
+
Not True is False
−
Not False is True
+
Not False is True
 +
 
 +
this() and not that()</nowiki>
 +
 
 
==Conditional Statements==
 
==Conditional Statements==
 
:if, else, and elif.
 
:if, else, and elif.
Line 152: Line 195:
 
   
 
   
 
  clinic()
 
  clinic()
 +
 +
===not in, or, and, is===
 +
some comparisons that can be used are:
 +
====not in====
 +
<nowiki>if var not in range(x):</nowiki>
 +
====or====
 +
<nowiki>if var == x or var == y:</nowiki>
 +
====and====
 +
<nowiki>if var == x and var == y:</nowiki>
 +
====is====
 +
<nowiki>if var is x:</nowiki>
  
 
=datetime=
 
=datetime=
Line 195: Line 249:
 
   return min(args)</nowiki>
 
   return min(args)</nowiki>
 
===abs()===
 
===abs()===
−
absolute value from 0.
+
absolute value from 0. if the number is a fraction, this will make it whole.
 
  <nowiki>ie.
 
  <nowiki>ie.
 
print abs(5)
 
print abs(5)
 
>5</nowiki>
 
>5</nowiki>
 +
===round()===
 +
rounded value of number.
 +
<nowiki>ie.
 +
print round(10.5)
 +
>11</nowiki>
 
===type()===
 
===type()===
 
returns the type of data in the argument. (ie, is it an '''int''' or '''float''' or '''string''', etc)
 
returns the type of data in the argument. (ie, is it an '''int''' or '''float''' or '''string''', etc)
Line 216: Line 275:
 
extend the length of a list, you can also add multiple items natively.
 
extend the length of a list, you can also add multiple items natively.
 
  <nowiki>suitcase.extend(["bathing suit", "towel", "sunscreen"])</nowiki>
 
  <nowiki>suitcase.extend(["bathing suit", "towel", "sunscreen"])</nowiki>
 +
 +
===index()===
 +
search for an item in a list
 +
<nowiki>animals = ["ant", "bat", "cat"]
 +
print animals.index("bat")</nowiki>
 +
 +
===insert()===
 +
insert an item into a specific list position, shifting any existing items.
 +
<nowiki>animals = ["ant", "bat", "cat"]
 +
animals.insert(1, "dog")
 +
print animals
 +
> ["ant", "dog", "bat", "cat"]</nowiki>
 +
 +
===sort()===
 +
sort a list smallest to largest, can be either numbers or letters.
 +
<nowiki>function.sort()</nowiki>
 +
 +
===remove()===
 +
remove item from a list.
 +
<nowiki>listname.remove('value')
 +
ie. backpack.remove('dagger')</nowiki>
 +
 +
===range()===
 +
generates a list
 +
====range(stop)====
 +
stops at the specified interval
 +
<nowiki>range(6) # => [0, 1, 2, 3, 4, 5]</nowiki>
 +
====range(start,stop)====
 +
starts and stops at the specified intervals
 +
<nowiki>range(1, 6) # => [1, 2, 3, 4, 5]</nowiki>
 +
====range(start,stop,step)====
 +
starts and stops at the specified intervals within a specific iteration.
 +
<nowiki>range(1, 6, 3) # => [1, 4]</nowiki>
 +
You can also count backwards
 +
<nowiki>range(100,-1,-1) # starts at 100 and goes to 0, stopping at -1</nowiki>
  
 
=Modules=
 
=Modules=
Line 234: Line 328:
 
  <nowiki>import math
 
  <nowiki>import math
 
print dir(math)</nowiki>
 
print dir(math)</nowiki>
 +
 +
=Loops=
 +
==For loops==
 +
very similar to other scripting languages.  Looping through a list will begin with the 0th element and go to the last.
 +
<nowiki> for future_var in list
 +
ie.
 +
numbers [1, 2, 3]
 +
for x in numbers
 +
  print x</nowiki>
 +
===dictionary loop===
 +
dictionaries are unordered, so every time you loop through, it will go in a different order.
 +
<nowiki>d = {"foo" : "bar"}
 +
for key in d:
 +
  print d[key]</nowiki>
 +
 +
===counted loop===
 +
sometimes you need to loop through a list and run a series of actions against each element individually
 +
<nowiki>n = [3, 5, 7]
 +
for i in range(0, len(n)):
 +
  n[i] = n[i] * 2</nowiki>
 +
===implicit loops===
 +
Another way to do this is with an implicit count.  notice how <code>num</code> is never defined nor is there a defined method to increase the num value.
 +
<nowiki>hobbies = []
 +
 +
for num in range(3):
 +
  hobby =  raw_input("Tell me one of your favorite hobbies: ")
 +
  hobbies.append(hobby)
 +
 +
print hobbies</nowiki>
 +
 +
 +
You can also do a similar method for printing individual characters in a string.
 +
<nowiki>word = "eggs!"
 +
 +
# Your code here!
 +
for c in word:
 +
  print c</nowiki>
 +
 +
===Enumerate===
 +
This function supplies a corresponding index to each element in a list.
 +
<nowiki>choices = ['pizza', 'pasta', 'salad', 'nachos']
 +
 +
print 'Your choices are:'
 +
for index, item in enumerate(choices):
 +
  print index, item</nowiki>
 +
 +
===Multiple lists with zip===
 +
This allows you to iterate over multiple lists at the same time.
 +
<nowiki>list_a = [3, 9, 17, 15, 19]
 +
list_b = [2, 4, 8, 10, 30, 40, 50, 60, 70, 80, 90]
 +
 +
for a, b in zip(list_a, list_b):
 +
  print a + " " + b</nowiki>
 +
==While Loop==
 +
Loops until the condition is met.
 +
<nowiki>while True:
 +
  print count
 +
  count += 1
 +
  if count >= 10:
 +
    break</nowiki>
 +
 +
=Dictionaries=
 +
Dictionaries use key-value pairs which allow a common (or uncommon) association of values. key-value pairs can be any string or number.<br>
 +
''You can also add lists into dictionaries.''
 +
<nowiki>d = {'key1' : 'value1', 'key2' : 'value2', 'key3' : 'value3'}</nowiki>
 +
<nowiki>ie.
 +
residents = {'Puffin' : 104, 'Sloth' : 105, 'Burmese Python' : 106}
 +
for animal in residents:
 +
  if animal in ('Sloth','Burmese Python'):
 +
    print residents[animal]
 +
> 105
 +
> 106</nowiki>
 +
 +
<nowiki>my_dict = {
 +
  "Crypto": "ETH",
 +
  "Balance": 3.092,
 +
  "Value": 4200
 +
}
 +
for key in my_dict:
 +
  print key, my_dict[key]
 +
 +
>Balance 3.092
 +
Crypto ETH
 +
Value 4200</nowiki>
 +
 +
==keys and values==
 +
print an array of tuples with each tuple consisting of a key/value pair.
 +
<nowiki>print dictionary.items()</nowiki>
 +
print the dictionaries keys or values.  these will NOT print in any specific order.
 +
<nowiki>print dictionary.keys()
 +
print dictionary.values()</nowiki>
 +
 +
==adding to dictionary==
 +
to add to an existing dictionary
 +
<nowiki>dict_name[new_key] = new_value
 +
menu['Spam'] = 2.50</nowiki>
 +
 +
==deleting from dictionary==
 +
===single===
 +
to delete a single entry its easy.
 +
<nowiki>del dict_name[key_name]
 +
ie. del num_list[num_1]</nowiki>
 +
===multiple===
 +
Alternatively, if you need to delete multiple entries from a dictionary, it becomes a bit trickier as you can't loop using the dictionary you are modifying.  If you do, you'll encounter an error because the dictionary size changes during iteration. <br>
 +
A solution to this is creating a list of the items to be deleted.
 +
<nowiki>ie.
 +
zoo_animals = { 'Unicorn' : 'Cotton Candy House',
 +
'Sloth' : 'Rainforest Exhibit',
 +
'Bengal Tiger' : 'Jungle House',
 +
'Atlantic Puffin' : 'Arctic Exhibit',
 +
'Rockhopper Penguin' : 'Arctic Exhibit'}
 +
 +
dead_animals = ('Sloth', 'Bengal Tiger')
 +
for animal in dead_animals:
 +
  if zoo_animals.has_key(animal):
 +
    del zoo_animals[animal]</nowiki>
 +
The above will loop through the list called '''dead_animals''', then look in the  '''zoo_animals''' dictionary for any matching keys, and if found, delete the key from '''zoo_animals'''.
 +
 +
=Examples=
 +
==Is Integer==
 +
determine if X is an integer
 +
<nowiki>def is_int(x):
 +
  absolute = abs(x)
 +
  rounded = round(absolute)
 +
  if absolute - rounded == 0:
 +
    return True
 +
  else:
 +
    return False
 +
 +
print is_int(10)
 +
print is_int(10.5)</nowiki>
 +
 +
==Add digits==
 +
Take each individual number from a number and add them together (ie. 1234 = 1+2+3+4 = 10)
 +
<nowiki>def digit_sum(n):
 +
  total = 0
 +
  print "number: " + str(n)
 +
  for i in str(n):
 +
    print i
 +
    total += int(i)
 +
  print "total: " + str(total)
 +
  return total</nowiki>
 +
 +
==Determine Factorial==
 +
Calculate the factorial of a non-negative integer.
 +
<nowiki>def factorial(x):
 +
    total = 1
 +
    while x>0:
 +
        total *= x
 +
        x-=1
 +
    return total
 +
 
 +
print factorial(5)</nowiki>
 +
 +
==Prime number==
 +
Determine if x is a prime number.
 +
<nowiki>def is_prime(x):
 +
  if x < 2:
 +
    return False
 +
  else:
 +
    for n in range(2,x-1):
 +
      if x % n == 0:
 +
        return False
 +
    else:
 +
      return True</nowiki>
 +
 +
==reverse letters in word==
 +
<nowiki>def reverse(text):
 +
  print "text: " + str(text)
 +
  for letter in range(len(text)-1,-1,-1):
 +
    if letter == len(text)-1:
 +
      output = text[letter]
 +
    else:
 +
      output += str(text[letter])
 +
  print output
 +
  return output</nowiki>
 +
 +
==strip vowels from string==
 +
<nowiki>def anti_vowel(text):
 +
  vowels = ["a", "e", "i", "o", "u", "A", "E", "I", "O", "U"]
 +
  newString = ""
 +
  for i in range(len(text)):
 +
    if text[i] not in vowels:
 +
      newString += text[i]
 +
  return newString</nowiki>
 +
 +
==scrabble score==
 +
Using a dictionary list for letters and their corresponding values, take a word, make the letters lowercase, then determine the total score of the word.
 +
<nowiki>score = {"a": 1, "c": 3, "b": 3, "e": 1, "d": 2, "g": 2,
 +
        "f": 4, "i": 1, "h": 4, "k": 5, "j": 8, "m": 3,
 +
        "l": 1, "o": 1, "n": 1, "q": 10, "p": 3, "s": 1,
 +
        "r": 1, "u": 1, "t": 1, "w": 4, "v": 4, "y": 4,
 +
        "x": 8, "z": 10}
 +
 +
def scrabble_score(word):
 +
  result = 0
 +
  for letter in word:
 +
    letter = letter.lower()
 +
    if letter in score:
 +
      print "letter found: " + str(letter) + " with score: " + str(score[letter])
 +
      result += int(score[letter])
 +
  print result
 +
  return result</nowiki>
 +
 +
==censor word==
 +
censor word in a string with a series of asterisks that match the word letter count.
 +
<nowiki>def censor(text, word):
 +
  censor = ""
 +
  if word in text:
 +
    for i in range(len(word)):
 +
      censor += "*"
 +
    result = text.replace(word,censor)
 +
    print result
 +
    return result</nowiki>
 +
 +
==median==
 +
determine the median of a list.  if even, take the (2) numbers around the median position and average them together.  make sure the list is sorted before getting the median.
 +
<nowiki>def median(lst):
 +
  lst = sorted(lst)
 +
  if len(lst) % 2 == 0:
 +
    b = lst[len(lst) / 2]
 +
    c = lst[len(lst) / 2 - 1]
 +
    return float(b + c) / 2
 +
  else:
 +
    if len(lst) == 1:
 +
      return lst[0]
 +
    else:
 +
      return lst[len(lst) / 2]</nowiki>

Latest revision as of 01:52, 11 May 2021

Contents

[edit] reserved words

These are some words that you should not use in python as they are reserved.

list
reserved word that should not be used as a variable name.

[edit] 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

[edit] 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.

[edit] convert int to string

age = 13
print str(age)

[edit] convert string to int

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

[edit] convert to float

n1 = "7.5"
print float(n1)

[edit] verify is alpha (letters) only

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

[edit] arithmetic operators

[edit] add/subtract/multiply/divide/exponentiation/modulo

[edit] exponentiation (exponential, similar to square roots)

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

[edit] modulo (remainder)

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

[edit] shorthand

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

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

[edit] comments

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

[edit] print

[edit] display output

print "Hello World"

[edit] display specific letter, left to right, 0 forward

print "TEST"[0] = "T"

[edit] trailing comma

adding a trailing comma ensures that we keep printing on the same line. 

print number,

[edit] strings

[edit] multi-line string

for strings that span multiple lines, use triple quotes 
address_string = """136 Whowho Rd
Apt 7
Whosville, WZ 44494"""

[edit] 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)

[edit] string methods

len() ; lower() ; upper() ; str()

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

len(length)   =   6

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

LOWERCASE.lower()   =   lowercase

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

uppercase.upper()   =   UPPERCASE

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

str(3.14)   =   "3.14"

[edit] 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)

[edit] 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.

[edit] 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:"))

[edit] slice

parse certain characters from a variable 
x=variable
 print x[1:3]
 ari
 
 x=variable
 print [3:len(x)]
 iable

slicing a string can be tricky too. think about this example [:3], this says to slice characters 0 through 3 from the string, however it does not include 3. the key to the logic is the word upto, we are slicing from 0 upto 3. In otherwords, if you think about it as a fraction, we slice from 0 to 2.9999..., so it would NOT be inclusive of the 3rd character.
this is also why if we do [3:] that would be from, we are slicing from 3 to the end of the string, ie. 3+, so it would be inclusive of the 3rd character.

[edit] 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 = []

[edit] Access by Index

You can access individual items, starting from 0. 

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

[edit] slicing

slicing lists is a bit weird compared to accessing by index. Rather than starting at 0, you actually start at 1 when calling multiple items. 

ie. letters = ['a', 'b', 'c', 'd']
first_pair = letters [0:2]
second_pair = letters [3:4]

if you try to start at 0, it prints out an empty list. 

print letters [0:0]
> []

I'm not sure why it behaves like this.

[edit] removing

There are a few different ways to remove items from lists.

[edit] .pop()

returns the item being removed and then removes it from the list. 

n = [1, 3, 5]
n.pop(1)
# Returns 3 (the item at index 1)
print n
# prints [1, 5]

[edit] .remove()

removes the actual item if found 

n.remove(1)
# Removes 1 from the list,
# NOT the item at index 1
print n
# prints [3, 5]

[edit] del()

deletes the item at the given index 

del(n[1])
# Doesn't return anything
print n
# prints [1, 5]

[edit] Generating Examples

Generate a list of even numbers from 0-51 

evens_to_50 = [i for i in range(51) if i % 2 == 0]

Double numbers 

doubles = [x * 2 for x in range(1, 6)]

[edit] 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!'

[edit] Comparators

[edit] basic comparisons

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

[edit] 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.

[edit] Boolean Operators

and, or, or not

[edit] 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

this() and not that()

[edit] 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()

[edit] not in, or, and, is

some comparisons that can be used are:

[edit] not in

if var not in range(x):

[edit] or

if var == x or var == y:

[edit] and

if var == x and var == y:

[edit] is

if var is x:

[edit] datetime

builtin function within python with date time variable.

[edit] print

print datetime.now()

[edit] manipulate

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

[edit] functions

functions are defined using def 

ie. def my_function()

[edit] parameters

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

ie def my_function(var_a, var_b, var_c)

[edit] 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

[edit] Python baked in functions

[edit] max()

returns the largest number from X arguments 

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

[edit] min()

opposite of max, gives the smallest number from X arguments 

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

[edit] abs()

absolute value from 0. if the number is a fraction, this will make it whole. 

ie.
print abs(5)
>5

[edit] round()

rounded value of number. 

ie.
print round(10.5)
>11

[edit] 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_)

[edit] append()

append a single (1) item to a list. You cannot use append() to add more than a single item at a time without outside help. 

list.append(1)

[edit] extend()

extend the length of a list, you can also add multiple items natively. 

suitcase.extend(["bathing suit", "towel", "sunscreen"])

[edit] index()

search for an item in a list 

animals = ["ant", "bat", "cat"]
print animals.index("bat")

[edit] insert()

insert an item into a specific list position, shifting any existing items. 

animals = ["ant", "bat", "cat"]
animals.insert(1, "dog")
print animals
> ["ant", "dog", "bat", "cat"]

[edit] sort()

sort a list smallest to largest, can be either numbers or letters. 

function.sort()

[edit] remove()

remove item from a list. 

listname.remove('value')
ie. backpack.remove('dagger')

[edit] range()

generates a list

[edit] range(stop)

stops at the specified interval 

range(6) # => [0, 1, 2, 3, 4, 5]

[edit] range(start,stop)

starts and stops at the specified intervals 

range(1, 6) # => [1, 2, 3, 4, 5]

[edit] range(start,stop,step)

starts and stops at the specified intervals within a specific iteration. 

range(1, 6, 3) # => [1, 4]

You can also count backwards 

range(100,-1,-1) # starts at 100 and goes to 0, stopping at -1

[edit] Modules

[edit] 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 *

[edit] List all functions from a module

import math
print dir(math)

[edit] Loops

[edit] For loops

very similar to other scripting languages. Looping through a list will begin with the 0th element and go to the last. 

 for future_var in list
ie.
numbers [1, 2, 3]
for x in numbers
  print x

[edit] dictionary loop

dictionaries are unordered, so every time you loop through, it will go in a different order. 

d = {"foo" : "bar"}
for key in d:
  print d[key]

[edit] counted loop

sometimes you need to loop through a list and run a series of actions against each element individually 

n = [3, 5, 7]
for i in range(0, len(n)):
  n[i] = n[i] * 2

[edit] implicit loops

Another way to do this is with an implicit count. notice how num is never defined nor is there a defined method to increase the num value. 

hobbies = []

for num in range(3):
  hobby =  raw_input("Tell me one of your favorite hobbies: ")
  hobbies.append(hobby)

print hobbies


You can also do a similar method for printing individual characters in a string. 

word = "eggs!"

# Your code here!
for c in word:
  print c

[edit] Enumerate

This function supplies a corresponding index to each element in a list. 

choices = ['pizza', 'pasta', 'salad', 'nachos']

print 'Your choices are:'
for index, item in enumerate(choices):
  print index, item

[edit] Multiple lists with zip

This allows you to iterate over multiple lists at the same time. 

list_a = [3, 9, 17, 15, 19]
list_b = [2, 4, 8, 10, 30, 40, 50, 60, 70, 80, 90]

for a, b in zip(list_a, list_b):
  print a + " " + b

[edit] While Loop

Loops until the condition is met. 

while True:
  print count
  count += 1
  if count >= 10:
    break

[edit] Dictionaries

Dictionaries use key-value pairs which allow a common (or uncommon) association of values. key-value pairs can be any string or number.
You can also add lists into dictionaries. 

d = {'key1' : 'value1', 'key2' : 'value2', 'key3' : 'value3'}
ie.
residents = {'Puffin' : 104, 'Sloth' : 105, 'Burmese Python' : 106}
for animal in residents:
  if animal in ('Sloth','Burmese Python'):
    print residents[animal]
> 105
> 106

my_dict = {
  "Crypto": "ETH",
  "Balance": 3.092,
  "Value": 4200
}
for key in my_dict:
  print key, my_dict[key]

>Balance 3.092
Crypto ETH
Value 4200

[edit] keys and values

print an array of tuples with each tuple consisting of a key/value pair. 

print dictionary.items()

print the dictionaries keys or values. these will NOT print in any specific order. 

print dictionary.keys()
print dictionary.values()

[edit] adding to dictionary

to add to an existing dictionary 

dict_name[new_key] = new_value
menu['Spam'] = 2.50

[edit] deleting from dictionary

[edit] single

to delete a single entry its easy. 

del dict_name[key_name]
ie. del num_list[num_1]

[edit] multiple

Alternatively, if you need to delete multiple entries from a dictionary, it becomes a bit trickier as you can't loop using the dictionary you are modifying. If you do, you'll encounter an error because the dictionary size changes during iteration.
A solution to this is creating a list of the items to be deleted. 

ie.
zoo_animals = { 'Unicorn' : 'Cotton Candy House',
'Sloth' : 'Rainforest Exhibit',
'Bengal Tiger' : 'Jungle House',
'Atlantic Puffin' : 'Arctic Exhibit',
'Rockhopper Penguin' : 'Arctic Exhibit'}

dead_animals = ('Sloth', 'Bengal Tiger')
for animal in dead_animals:
  if zoo_animals.has_key(animal):
    del zoo_animals[animal]

The above will loop through the list called dead_animals, then look in the zoo_animals dictionary for any matching keys, and if found, delete the key from zoo_animals.

[edit] Examples

[edit] Is Integer

determine if X is an integer 

def is_int(x):
  absolute = abs(x)
  rounded = round(absolute)
  if absolute - rounded == 0:
    return True
  else:
    return False

print is_int(10)
print is_int(10.5)

[edit] Add digits

Take each individual number from a number and add them together (ie. 1234 = 1+2+3+4 = 10) 

def digit_sum(n):
  total = 0
  print "number: " + str(n)
  for i in str(n):
    print i
    total += int(i)
  print "total: " + str(total)
  return total

[edit] Determine Factorial

Calculate the factorial of a non-negative integer. 

def factorial(x):
    total = 1
    while x>0:
        total *= x
        x-=1
    return total
  
print factorial(5)

[edit] Prime number

Determine if x is a prime number. 

def is_prime(x):
  if x < 2:
    return False
  else:
    for n in range(2,x-1):
      if x % n == 0:
        return False
    else:
      return True

[edit] reverse letters in word

def reverse(text):
  print "text: " + str(text)
  for letter in range(len(text)-1,-1,-1):
    if letter == len(text)-1:
      output = text[letter]
    else:
      output += str(text[letter])
  print output
  return output

[edit] strip vowels from string

def anti_vowel(text):
  vowels = ["a", "e", "i", "o", "u", "A", "E", "I", "O", "U"]
  newString = ""
  for i in range(len(text)):
    if text[i] not in vowels:
      newString += text[i]
  return newString

[edit] scrabble score

Using a dictionary list for letters and their corresponding values, take a word, make the letters lowercase, then determine the total score of the word. 

score = {"a": 1, "c": 3, "b": 3, "e": 1, "d": 2, "g": 2, 
         "f": 4, "i": 1, "h": 4, "k": 5, "j": 8, "m": 3, 
         "l": 1, "o": 1, "n": 1, "q": 10, "p": 3, "s": 1, 
         "r": 1, "u": 1, "t": 1, "w": 4, "v": 4, "y": 4, 
         "x": 8, "z": 10}

def scrabble_score(word):
  result = 0
  for letter in word:
    letter = letter.lower()
    if letter in score:
      print "letter found: " + str(letter) + " with score: " + str(score[letter])
      result += int(score[letter])
  print result
  return result

[edit] censor word

censor word in a string with a series of asterisks that match the word letter count. 

def censor(text, word):
  censor = ""
  if word in text:
    for i in range(len(word)):
      censor += "*"
    result = text.replace(word,censor)
    print result
    return result

[edit] median

determine the median of a list. if even, take the (2) numbers around the median position and average them together. make sure the list is sorted before getting the median. 

def median(lst):
  lst = sorted(lst)
  if len(lst) % 2 == 0:
    b = lst[len(lst) / 2]
    c = lst[len(lst) / 2 - 1]
    return float(b + c) / 2
  else:
    if len(lst) == 1:
      return lst[0]
    else:
      return lst[len(lst) / 2]
Retrieved from "https://wiki.r00tedvw.com/index.php?title=Python/Basic_Code&oldid=3188"
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