Difference between revisions of "Python: Basics"
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− | + | * Single-line comment | |
− | |||
<pre> | <pre> | ||
# Hello World | # Hello World | ||
</pre> | </pre> | ||
− | + | * Multiple-line comment | |
<pre> | <pre> | ||
""""Hello | """"Hello | ||
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<pre> | <pre> | ||
.isalpha() # Check if alpha characters | .isalpha() # Check if alpha characters | ||
− | <pre> | + | </pre> |
* Create a function | * Create a function | ||
<pre> | <pre> | ||
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my_list.sort() | my_list.sort() | ||
</pre> | </pre> | ||
− | + | ||
− | + | Remove item from the list | |
+ | * 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] | ||
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# prints [1, 5] | # prints [1, 5] | ||
</pre> | </pre> | ||
− | + | * n.remove(item) will remove the actual item if it finds it: | |
<pre> | <pre> | ||
n.remove(1) | n.remove(1) | ||
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# 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: | |
<pre> | <pre> | ||
del(n[1]) | del(n[1]) | ||
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return data[city] | return data[city] | ||
</pre> | </pre> | ||
− | + | Remove item in dictionary | |
− | + | * 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. | |
<pre> | <pre> | ||
my_list.remove(value) | my_list.remove(value) | ||
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</pre> | </pre> | ||
− | * Random | + | * Random module |
<pre> | <pre> | ||
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print a, b | print a, b | ||
</pre> | </pre> | ||
+ | |||
+ | [[Category:Python]] |
Latest revision as of 13:42, 20 October 2013
- Single-line comment
# Hello World
- Multiple-line comment
""""Hello World"""
- Functions
.isalpha() # Check if alpha characters
- Create a function
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 module
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