NUMBERS
max() |
returns largest argument of list |
min() |
returns smallest argument of list |
abs() |
returns absolute value of argument |
type() |
return data type of argument |
STRINGS
Create Strings |
'string' |
creates string |
"string" |
creates string |
String Methods |
print( ) |
("hello"), (variable) |
g = "Golf"
h = "Hotel"
print("%s, %s" % (g, h))
print("My name is {0}".format('Fred')) |
str(3) |
returns "3", not #3 |
len("string") |
returns 5 |
"string".upper() |
returns 'STRING' |
"STRING".lower() |
returns 'string' |
word[0] |
returns "w" |
word[1:len(word)] |
returns "ord" |
LOOPING
For loops for variable in sequence :
for x in range(1, 10):
print(x)
The variable will iterate through each item in the sequence. |
If if condition :
if x == 7:
print(x)
The following lines are only executed if the condition is true. The condition can be either a single comparison, eg. 5 > 3, or multiple comparisons using Boolean operators to evaluate ultimate True or False eg. 1<2 and 2<3 (returns True, so the following lines are evaluated) |
elif elif condition :
provides second if test, when first if test is false: elif x == 5:
print(x)
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else (runs if the if/elif test is false)
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while while condition :
Remains in the loop while the condition is true. Use the "break" command to leave the loop. This is useful if waiting on an input from microcontroller. Once the microcontroller input is received, the break command kicks out of the loop and continues with the program.
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FUNCTION STRUCTURE
def shut_down(s):
if s == "yes":
return "shutting down"
elif s == "no":
return "Shutdown aborted"
else:
return "Sorry"
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def is_numeric(num):
return type(num) == int or
type(num) == float:
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def finish_game(score):
tickets = 10 * score
if score >= 10:
tickets += 50
elif score >= 7:
tickets += 20
return tickets
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IMPORTING MODULES & FUNCTIONS
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import math makes math module available
usage: math.sqrt()
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from math import * imports all math functions into program
usage: sqrt()
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from math import sqrt imports only the math function specified
usage: sqrt()
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READING & WRITING FILES
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variable to hold file |
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reads the file |
output = open(to_file, 'w')
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open file to write to, 'w' makes file writable |
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finish by closing to_file
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example: exercise 17 in the book Python The Hard Way (page 43).
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LISTS
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list_name = [item_1, item_2] Items can be 'strings', variables, integers, etc.
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List Index use the index to access specific locations usage: list_name[0] #first entry
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Add to Lists: .append use .append to add a new entry to the end of the List; note the use of ( ) list_name.append('string')
adds 'string' to end of the list contents |
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Add to Lists: assignment replace an item in a List: list_name[4] = 'string'
replaces 5th item in list with 'string' |
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Adding Lists together list_A = [1,2,3]
list_B = [4,5]
list_C = list_A + list_B
print(list_C) #returns [1,2,3,4,5]
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len(list_name) returns the number of items in the list
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print (list_name) returns [item_1, item_2, etc.]
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List Slicing letters = ['a', 'b', 'c', 'd']
slice = letters[1:3]
print slice #returns ['b', 'c']
[1:3]
means this will return entries starting at index 1 and continue up to, but not including the third index position |
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List Slicing with Strings strings are considered to be natural lists, with each letter being an item of the list animal = 'blueWhale'
print = (animal[4:]) #returns Whale
print = (animal[:4]) #returns blue
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List Manipulation .index letters = ['a', 'b', 'c']
print(letters.index('b')) #prints 1
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List Manipulation .sort numbers = [5, 3, 7]
print(numbers.sort()) #prints [3,5,7]
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List Manipulation .pop numbers = [5, 3, 7]
print(numbers.pop()) #no index pops last item
#prints 7, and removes it from the list
print(numbers.pop(1)) #pops second item
#prints 3, and removes it from the list
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List Manipulation .insert numbers = [5, 3, 7]
print(numbers.insert(1,9)) #prints [5,9,3,7]
inserts the number 9 "before" position 1 in the list |
Dictionaries
ph_numbers = {'Jack':x123, 'Mark':x655}
ph_numbers['Mark']
#returns x655
ph_numbers['Mark'] = x899 #assigns new number
ph_numbers
#returns {'Jack':x123, 'Mark'=x899}
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A dictionary is comprised of both a "key" and a "value". You access or reassign a particular value by using the key, NOT the position. The dictionary does not maintain a specific order to any of its entries.
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