Difference between revisions of "Python: Basics"
Jump to navigation
Jump to search
(Created page with "* Comment ** Single-line comment <pre> # Hello World </pre> ** Multiple-line comment <pre> """"Hello World""" </pre> * Functions <pre> .isalpha() # Check if alpha ...") |
|||
Line 1: | Line 1: | ||
* Comment | * Comment | ||
− | + | ** Single-line comment | |
− | ** Single-line comment | ||
− | |||
<pre> | <pre> | ||
− | |||
# Hello World | # Hello World | ||
− | |||
</pre> | </pre> | ||
− | |||
** Multiple-line comment | ** Multiple-line comment | ||
− | |||
<pre> | <pre> | ||
− | |||
""""Hello | """"Hello | ||
− | |||
World""" | World""" | ||
− | |||
</pre> | </pre> | ||
− | |||
* Functions | * Functions | ||
− | |||
<pre> | <pre> | ||
− | + | .isalpha() # Check if alpha characters | |
− | .isalpha() | ||
− | |||
<pre> | <pre> | ||
− | |||
* Create a function | * Create a function | ||
− | |||
<pre> | <pre> | ||
− | |||
def <function_name> (): | def <function_name> (): | ||
Line 40: | Line 24: | ||
sum(args) # You add arguments up | sum(args) # You add arguments up | ||
− | |||
</pre> | </pre> | ||
* Import defined functions | * Import defined functions | ||
− | |||
<pre> | <pre> | ||
− | |||
from <module> import <function> | from <module> import <function> | ||
− | |||
Sample: | Sample: | ||
+ | import math # Import all, use math.sqrt | ||
+ | math import sqrt # Import only sqrt, no need to qualify | ||
+ | from math import * # Just import metadata?? | ||
− | + | import this # Easter Egg - The Zen of Python | |
− | |||
− | |||
− | |||
− | |||
− | |||
− | import this | ||
− | |||
</pre> | </pre> | ||
− | |||
* If-then-else on one line | * If-then-else on one line | ||
− | |||
<pre> | <pre> | ||
− | |||
Boolean = True if (1 == 2) else False | Boolean = True if (1 == 2) else False | ||
if : | if : | ||
− | |||
elif : | elif : | ||
− | |||
else: | else: | ||
− | |||
</pre> | </pre> | ||
* List | * List | ||
− | |||
<pre> | <pre> | ||
− | |||
<list_name> = [] # Empty list | <list_name> = [] # Empty list | ||
− | |||
<list_name>.append(<item>) | <list_name>.append(<item>) | ||
− | |||
</pre> | </pre> | ||
* List samples | * List samples | ||
− | |||
<pre> | <pre> | ||
− | |||
my_list.index("dog") # Return the first index that contains the string “dog” | my_list.index("dog") # Return the first index that contains the string “dog” | ||
− | |||
my_list.insert(4,"cat") # Add item “cat” at index 4 and bump the rest forward | my_list.insert(4,"cat") # Add item “cat” at index 4 and bump the rest forward | ||
− | |||
</pre> | </pre> | ||
* For loop the list | * For loop the list | ||
− | |||
<pre> | <pre> | ||
− | |||
my_list = [1,9,3,8,5,7] | my_list = [1,9,3,8,5,7] | ||
− | |||
for number in my_list: | for number in my_list: | ||
− | + | print number * 2 | |
− | |||
my_list.sort() | my_list.sort() | ||
− | |||
</pre> | </pre> | ||
− | |||
* Remove item from the list | * Remove item from the list | ||
− | |||
** n.pop(index) will remove the item at index from the list and return it to you: | ** n.pop(index) will remove the item at index from the list and return it to you: | ||
− | |||
<pre> | <pre> | ||
− | |||
n = [1, 3, 5] | n = [1, 3, 5] | ||
n.pop(1) | n.pop(1) | ||
Line 121: | Line 74: | ||
# prints [1, 5] | # prints [1, 5] | ||
</pre> | </pre> | ||
− | |||
** n.remove(item) will remove the actual item if it finds it: | ** n.remove(item) will remove the actual item if it finds it: | ||
− | |||
<pre> | <pre> | ||
− | |||
n.remove(1) | n.remove(1) | ||
# Removes 1 from the list, | # Removes 1 from the list, | ||
Line 132: | Line 82: | ||
# prints [3, 5] | # prints [3, 5] | ||
</pre> | </pre> | ||
− | |||
** del(n[1] is like .pop in that it will remove the item at the given index, but it won't return it: | ** del(n[1] is like .pop in that it will remove the item at the given index, but it won't return it: | ||
− | |||
<pre> | <pre> | ||
− | |||
del(n[1]) | del(n[1]) | ||
# Doesn't return anything | # Doesn't return anything | ||
print n | print n | ||
# prints [1, 5] | # prints [1, 5] | ||
− | |||
</pre> | </pre> | ||
* Dictionary | * Dictionary | ||
− | |||
<pre> | <pre> | ||
− | |||
d = {'key1' : 1, 'key2' : 2, 'key3' : 3} | d = {'key1' : 1, 'key2' : 2, 'key3' : 3} | ||
− | |||
</pre> | </pre> | ||
* Dictionary sample | * Dictionary sample | ||
− | |||
<pre> | <pre> | ||
− | |||
menu = {} # Empty dictionary | menu = {} # Empty dictionary | ||
− | |||
menu['Chicken Alfredo'] = 14.50 # Adding new key-value pair | menu['Chicken Alfredo'] = 14.50 # Adding new key-value pair | ||
def plane_ride_cost(city): | def plane_ride_cost(city): | ||
− | + | data = {"Charlotte": 183, "Tampa": 220, "Pittsburgh": 222, "Los Angeles": 475} | |
− | + | return data[city] | |
− | |||
</pre> | </pre> | ||
− | |||
* Remove item in dictionary | * Remove item in dictionary | ||
− | |||
** del deletes a key and its value based on the key you tell it to delete | ** del deletes a key and its value based on the key you tell it to delete | ||
− | |||
<pre> | <pre> | ||
− | |||
del dict_name[key_name] | del dict_name[key_name] | ||
− | |||
</pre> | </pre> | ||
− | |||
** .remove() removes a key and its value based on the value you tell it to delete. | ** .remove() removes a key and its value based on the value you tell it to delete. | ||
− | |||
<pre> | <pre> | ||
− | |||
my_list.remove(value) | my_list.remove(value) | ||
− | |||
</pre> | </pre> | ||
* More dictionary samples | * More dictionary samples | ||
− | |||
<pre> | <pre> | ||
− | |||
inventory = {'gold' : 500, | inventory = {'gold' : 500, | ||
− | |||
'pouch' : ['flint', 'twine', 'gemstone'], # Assigned a new list to 'pouch' key | 'pouch' : ['flint', 'twine', 'gemstone'], # Assigned a new list to 'pouch' key | ||
− | |||
'backpack' : ['xylophone','dagger', 'bedroll','bread loaf']} | 'backpack' : ['xylophone','dagger', 'bedroll','bread loaf']} | ||
# Adding a key 'burlap bag' and assigning a list to it | # Adding a key 'burlap bag' and assigning a list to it | ||
− | |||
inventory['burlap bag'] = ['apple', 'small ruby', 'three-toed sloth'] | inventory['burlap bag'] = ['apple', 'small ruby', 'three-toed sloth'] | ||
# Sorting the list found under the key 'pouch' | # Sorting the list found under the key 'pouch' | ||
− | |||
inventory['pouch'].sort() | inventory['pouch'].sort() | ||
− | |||
# Here the dictionary access expression takes the place of a list name | # Here the dictionary access expression takes the place of a list name | ||
inventory['pocket'] = ['seashell', 'strange berry', 'lint'] | inventory['pocket'] = ['seashell', 'strange berry', 'lint'] | ||
− | |||
inventory['backpack'].sort() | inventory['backpack'].sort() | ||
Line 211: | Line 133: | ||
inventory['gold'] = inventory['gold']+50 | inventory['gold'] = inventory['gold']+50 | ||
− | |||
</pre> | </pre> | ||
* Dictionaries are unordered | * Dictionaries are unordered | ||
− | |||
<pre> | <pre> | ||
− | |||
d => {"foo" : "bar"} | d => {"foo" : "bar"} | ||
− | for key in d: | + | for key in d: |
− | + | print d[key] # prints "bar" | |
</pre> | </pre> | ||
* Print vertically | * Print vertically | ||
− | |||
<pre> | <pre> | ||
− | |||
for letter in "Codecademy": | for letter in "Codecademy": | ||
− | + | print letter | |
− | |||
C | C | ||
Line 242: | Line 158: | ||
m | m | ||
y | y | ||
− | |||
</pre> | </pre> | ||
− | |||
<pre> | <pre> | ||
− | |||
def average(alist): | def average(alist): | ||
− | + | return sum(alist)/len(alist) | |
− | |||
score = round(score) | score = round(score) | ||
− | |||
</pre> | </pre> | ||
Line 258: | Line 169: | ||
<pre> | <pre> | ||
− | |||
from random import randrange | from random import randrange | ||
− | # Generate a | + | # Generate a |
− | |||
random_number = randrange(1, 10) | random_number = randrange(1, 10) | ||
− | |||
</pre> | </pre> | ||
* Enumerate | * Enumerate | ||
− | |||
<pre> | <pre> | ||
Line 274: | Line 181: | ||
print 'Your choices are:' | print 'Your choices are:' | ||
− | |||
for index, item in enumerate(choices): | for index, item in enumerate(choices): | ||
− | + | print index+1, item | |
− | |||
− | |||
</pre> | </pre> | ||
* Zip | * Zip | ||
− | |||
** It's also common to need to iterate over two lists at once. This is where the built-in zip function comes in handy. | ** It's also common to need to iterate over two lists at once. This is where the built-in zip function comes in handy. | ||
− | |||
** Zip will create pairs of elements when passed two lists, and will stop at the end of the shorter list. | ** Zip will create pairs of elements when passed two lists, and will stop at the end of the shorter list. | ||
− | |||
** Zip can handle three or more lists as well! | ** Zip can handle three or more lists as well! | ||
− | |||
<pre> | <pre> | ||
list_a = [3, 9, 17, 15, 19] | list_a = [3, 9, 17, 15, 19] | ||
− | |||
list_b = [2, 4, 8, 10, 30, 40, 50, 60, 70, 80, 90] | list_b = [2, 4, 8, 10, 30, 40, 50, 60, 70, 80, 90] | ||
for a, b in zip(list_a, list_b): | for a, b in zip(list_a, list_b): | ||
− | + | # Add your code here! | |
− | + | print a, b | |
− | |||
− | |||
− | |||
</pre> | </pre> |
Revision as of 18:08, 8 April 2013
- Comment
- Single-line comment
# Hello World
- Multiple-line comment
""""Hello World"""
- Functions
.isalpha() # Check if alpha characters <pre> * Create a function <pre> def <function_name> (): def <function_name> (arg): def <function_name> (arg1, arg2): def <function_name> (*args): # Multiple/unknown # of arguments, arbitrary number of arguments sum(args) # You add arguments up
- Import defined functions
from <module> import <function> Sample: import math # Import all, use math.sqrt math import sqrt # Import only sqrt, no need to qualify from math import * # Just import metadata?? import this # Easter Egg - The Zen of Python
- If-then-else on one line
Boolean = True if (1 == 2) else False if : elif : else:
- List
<list_name> = [] # Empty list <list_name>.append(<item>)
- List samples
my_list.index("dog") # Return the first index that contains the string “dog” my_list.insert(4,"cat") # Add item “cat” at index 4 and bump the rest forward
- For loop the list
my_list = [1,9,3,8,5,7] for number in my_list: print number * 2 my_list.sort()
- Remove item from the list
- n.pop(index) will remove the item at index from the list and return it to you:
n = [1, 3, 5] n.pop(1) # Returns 3 (the item at index 1) print n # prints [1, 5]
- n.remove(item) will remove the actual item if it finds it:
n.remove(1) # Removes 1 from the list, # NOT the item at index 1 print n # prints [3, 5]
- del(n[1] is like .pop in that it will remove the item at the given index, but it won't return it:
del(n[1]) # Doesn't return anything print n # prints [1, 5]
- Dictionary
d = {'key1' : 1, 'key2' : 2, 'key3' : 3}
- Dictionary sample
menu = {} # Empty dictionary menu['Chicken Alfredo'] = 14.50 # Adding new key-value pair def plane_ride_cost(city): data = {"Charlotte": 183, "Tampa": 220, "Pittsburgh": 222, "Los Angeles": 475} return data[city]
- Remove item in dictionary
- del deletes a key and its value based on the key you tell it to delete
del dict_name[key_name]
- .remove() removes a key and its value based on the value you tell it to delete.
my_list.remove(value)
- More dictionary samples
inventory = {'gold' : 500, 'pouch' : ['flint', 'twine', 'gemstone'], # Assigned a new list to 'pouch' key 'backpack' : ['xylophone','dagger', 'bedroll','bread loaf']} # Adding a key 'burlap bag' and assigning a list to it inventory['burlap bag'] = ['apple', 'small ruby', 'three-toed sloth'] # Sorting the list found under the key 'pouch' inventory['pouch'].sort() # Here the dictionary access expression takes the place of a list name inventory['pocket'] = ['seashell', 'strange berry', 'lint'] inventory['backpack'].sort() inventory['backpack'].remove('dagger') inventory['gold'] = inventory['gold']+50
- Dictionaries are unordered
d => {"foo" : "bar"} for key in d: print d[key] # prints "bar"
- Print vertically
for letter in "Codecademy": print letter C o d e c a d e m y
def average(alist): return sum(alist)/len(alist) score = round(score)
- Random modul
from random import randrange # Generate a random_number = randrange(1, 10)
- Enumerate
choices = ['pizza', 'pasta', 'salad', 'nachos'] print 'Your choices are:' for index, item in enumerate(choices): print index+1, item
- Zip
- It's also common to need to iterate over two lists at once. This is where the built-in zip function comes in handy.
- Zip will create pairs of elements when passed two lists, and will stop at the end of the shorter list.
- Zip can handle three or more lists as well!
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): # Add your code here! print a, b