View source for UTOSC 2008/90 percent of the Python you need to know (in 90 minutes)

Matt Harrison
http://panela.blog-city.com

The Zen of Python:
 import this

show memebers (attributes, functions) of instances:
 dir()

show docs for modules/classes/functions
 help()

 help("".zfill)

Variables can point to anything:
 my_var = "a string"
 my_var = 42  # an int

Number very similar to other languages.  No int overflow

Interpreter
 >>> 2.97 * 94.2
 279.774

Print variable
 nums=5
 nums

Strings:
 hello = 'hello'
 hello = "hello"
 hello = """this is a
   paragraph and she said "hi" and it was good"""

String formattting:
  var = "is %s " % "matt"
  var = "is %d " % 20

Functions of string?
 dir("")

Lists (mutable) and "tuples" (non-mutable)
 alpha = ["a", "b"]
 alpha.append("c")
 
 alpha = ("a", "b")

Functions of a list?
 dir([])

Slicing:
  alpha = ["a", "b", "c"]
  print alpha[0:1]  # 0 to 1
  print alpha[0:3:2]  # 0 to 3, every other one
  print alpha[1::2]  # ever other one

Range:
 range(5)  # generate numbers 0 to 4
 range(start, end, count)
 range(99, 1, -1)

Dictionaries (hash maps, or associated arrays)
 person = {"name": "bob", "age": 29}
 age = person["age"]

Functions of dictionary:
 dir({})

Functions:
 def my_func(param_1, param_2):
   """ doc string """
   return param_1 + param_2

Functions can have default values:
  def add(num, add=5):

Return true if gymnast older than 16:
 def is_16(year):
   return (2009 - year) >= 16

Conditionals:
 if x > 90:
   grade = "A"
 elif x > 80:
   grade = "B"
 else:
  grade = "C"

While (no switch - use dictionary):
 cap = {"utah": "salt lake", "arizona": "phoenix"}
 if state in capitals:
   print "cap of %s is %s" % (state, cap[state])
 else:
  print "not there"

Loops:
 for item in range(10):
   print item

Break out of loop with break and continue

Indexes, use enumerate;
 anim = ["a", "b", "c"]
 for index, value in enumerate(animals):
   print value, index

Return a list of numbers squared:
 def squared(numbers):
    results = []
    for num in numbers:
      results.append(num * num)
    return results

Open file:
 fin = open("food.txt")
 for line in fin:
   # do stuff
 fin.close();

Write to file:
 fout = open("bar.txt", "w")
 fout.write("hi")
 fout.close()

Comma at end of print statement won't add new line
 print "hi",

Print integers to file:
 fin.open("out.txt", "w")
 for i in range(100):
   fin.write(str(i))  # cast to string
 fin.close()

Class:
  class Hello(object):
    "doc string"
    
    # or
 
    """ 
      docs as paragraph
    """
 
    def __init__(self, name):
      self.name = name
 
    def talk(self):
      print "stuff"
 
    @staticmethod
    def main():
      print "Hello World"
 
 Hello.main()
 
 h = Hello("thing")
 h.talk()

Subclass:
  class hi(Hello):
    def talk(self):
       print "something else"

Try catch:
 try:
   ...
 except KeyError, e:
   ...
 except Exception, e:
   ...

Raise execption:
 raise Exception("my error")

== keywords ==

[[Category:Python]]
[[Category:Programming]]