Session 4 Homework

Students/salim/notes/class_notes.py

@@ -471,6 +471,12 @@ def complex_function(arg1, arg2, kwarg1=u'bannana'):
 
 ############################## SESSION03 ##############################
 
+"""
+making a python file an executable:
+    - change the mode of the file to executable: chmod +x myscript.py
+    - add the path to python at the top with '#!' before
+"""
+
 """
 git question:
     - create a pull request for the branch itself
@@ -643,3 +649,148 @@ def func(c, list=[]):   #  this is wrong because it dones't create a function le
     return list.append(c)
 
 
+############################## SESSION03 ##############################
+"""
+you almost never have to loop through sequences using range()
+- zip() will zip lists together
+- unpack embedded squences using this construct
+"""
+
+a_list = [(1,2), (3,4), (5,6)]
+
+for i, j in a_list:
+    print i
+    print j
+
+"""
+enumerate allows you to get the indix while you are looping through a sequence
+"""
+
+for i, item in enumerate(a_list):
+    print i
+    print item
+
+"""
+buidling up a long string:
+    - one option is to continue to keep += to the string. however, this is
+      an inefficent process
+    - a better way is to build a list, then use " ".join(list)
+
+sorting data:
+    - when you
+
+"""
+
+fruits = ['Apples', 'Pears', 'Grapes']
+numbers = [1, 2, 3]
+combine = zip(fruits, numbers)
+
+def sort_key(item):
+    return item[1]
+
+combine.sort(key=sort_key)
+
+"""
+you can build up strings for formatting before you subistiute values in
+"""
+
+s = 'Hello ' + '%d' * 4
+print s % (1,2,3,4)
+
+"""
+dictionaries:
+    - create a dict with d = {}
+    - keys don't have to be the same type and values don't have to be the same
+      type
+    - keys can be any immutable object (technically "hash" objects):
+        - number
+        - string
+        - tuple
+    - dictionaries are unordered (due to the way they are built using hasing)
+    - dictionaries are very effecicent
+
+dictionary methods
+    - dict.setdefault() <-- will use this in the homework
+    - dict.iteritems() <-- will not return a list
+
+hashing:
+    - missed this so read the class notes
+"""
+
+"""
+Exceptions:
+    - you can use "finally" at the end of an exception, which will always get
+      run
+    - they also have an "else" which will run if there is no exception
+"""
+# never do this!  this doesn't give you information about the exception
+try:
+    do_something()
+except:
+    print "something went wrong."
+
+"""
+reading and writing files:
+
+text files:
+    - f
+"""
+
+f = open('secrets.txt')
+secret_data = f.read()
+f.close()
+
+
+
+############################## SESSION04 ##############################
+
+""" dealing with "ordered" / "sorted" dicts """
+
+# option #1
+import collections   # package with tools for dealing with dicts
+o_dict = collections.OrderedDict()   # this will create an ordered dict
+
+# option #2
+sorted()   # built in function that sorts iterables
+
+""" Advanced argument passing """
+
+# keyword arguments
+def fun(a, b = True, c = False):
+    return
+
+# functional arguments
+
+def func(x, y, w=0, h=0):  # positional arguments are tuples
+                           # keywork arguments are dictionaries
+    print "%s %s %s %s" % (x, y, x, h)
+
+a_tuple = (1, 2)
+a_dict = {'w':1, 'h': 2}
+func(*a_tuple, **a_dict)  # you can pass the tuple and dict in directly
+
+def func(*args, **kwargs):  # you can recieve an undefined number of args
+    print args
+    print kwargs
+
+"""mutablility"""
+
+import copy   # for making copies of objects
+
+copy.deepcopy()   # this is how you make a deep copy
+
+
+"""list comprehensions"""
+l = [1, 2, 3]
+[i * 2 for i in l]
+[i * 2 for i in l if i > 1]  # you can have an if statement here
+
+# searching 'in' a sequence is faster with sets because they are hash tables
+
+"""set comprehension"""
+
+"""dict comprehensions"""
+
+
+"""testing in python"""
+

Students/salim/session03/list_lab.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python
 
+
 # print original list
 a_list = ['Apples', 'Pears', 'Oranges', 'Peaches']
 print a_list

Students/salim/session04/cp_dict_set_lab.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python
+
+
+# #############################Lesson 1##############################
+
+# create dict
+d1 = {'name': 'Chris', 'city': 'Seattle', 'cake': 'Chocolate'}
+print d1
+
+# delete entry for cake
+del d1['cake']
+print d1
+
+# add an entry to the dict
+d1['fruit'] = 'Mango'
+print d1
+
+# display the values
+d1.values()
+
+# display the keys
+d1.keys()
+
+# is 'cake' a key in the dict?
+'cake' in d1
+
+# is 'Mango' a value in the dict?
+'Mango' in d1.values()
+
+
+# #############################Lesson 2##############################
+
+# create list from 0 to 15
+l2 = range(16)
+
+# create list with hex representation
+s2 = []
+for item in l2:
+    s2.append(hex(item))
+
+# zip lists into dict
+d2 = dict(zip(l2, s2))
+
+
+# #############################Lesson 3##############################
+
+# use d1 to create a new dict with same keys but number of 't's in values
+d3 = {}
+for key, value in d1.iteritems():
+    d3[key] = value.count('t')
+
+
+# #############################Lesson 4##############################
+
+# make three sets
+s2 = set(range(0, 20, 2))
+s3 = set(range(0, 20, 3))
+s4 = set(range(0, 20, 4))
+
+# print the sets
+print s2
+print s3
+print s4
+
+# check sets
+s3.issubset(s2)
+s4.issubset(s2)
+
+
+# #############################Lesson 4##############################
+
+a_set = set('Python')
+a_set.add('i')
+
+b_set = frozenset('marathon')
+
+u_set = a_set.union(b_set)
+i_set = a_set.intersection(b_set)
+
+print u_set
+print i_set

Students/salim/session04/dict_set_lab.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python
+
+
+# #############################Lesson 1##############################
+
+# create dict
+d1 = {'name': 'Chris', 'city': 'Seattle', 'cake': 'Chocolate'}
+print d1
+
+# delete entry for cake
+del d1['cake']
+print d1
+
+# add an entry to the dict
+d1['fruit'] = 'Mango'
+print d1
+
+# display the values
+d1.values()
+
+# display the keys
+d1.keys()
+
+# is 'cake' a key in the dict?
+'cake' in d1
+
+# is 'Mango' a value in the dict?
+'Mango' in d1.values()
+
+
+# #############################Lesson 2##############################
+
+# create list from 0 to 15
+l2 = range(16)
+
+# create list with hex representation
+s2 = []
+for item in l2:
+    s2.append(hex(item))
+
+# zip lists into dict
+d2 = dict(zip(l2, s2))
+
+
+# #############################Lesson 3##############################
+
+# use d1 to create a new dict with same keys but number of 't's in values
+d3 = {}
+for key, value in d1.iteritems():
+    d3[key] = value.count('t')
+
+
+# #############################Lesson 4##############################
+
+# make three sets
+s2 = set(range(0, 20, 2))
+s3 = set(range(0, 20, 3))
+s4 = set(range(0, 20, 4))
+
+# print the sets
+print s2
+print s3
+print s4
+
+# check sets
+s3.issubset(s2)
+s4.issubset(s2)
+
+
+# #############################Lesson 4##############################
+
+a_set = set('Python')
+a_set.add('i')
+
+b_set = frozenset('marathon')
+
+u_set = a_set.union(b_set)
+i_set = a_set.intersection(b_set)
+
+print u_set
+print i_set

Students/salim/session04/exception_lab.py

@@ -0,0 +1,11 @@
+#!/usr/bin/env python
+
+
+def safe_input():
+    try:
+        return raw_input('Type ^c or ^d to raise an error.')
+    except (KeyboardInterrupt, EOFError):
+        return None
+
+if __name__ == '__main__':
+    safe_input()

Students/salim/session04/files_lab.py

@@ -0,0 +1,48 @@
+#!/Library/Frameworks/Python.framework/Versions/2.7/bin/python
+
+
+def read_file_to_list(a_file):
+    """Return a list of the lines in a file with newlines removed"""
+    # move file to begining
+    a_file.seek(0)
+
+    # add lines to list
+    a_list = []
+    for line in a_file:
+        a_list.append(line.strip())
+
+    return a_list
+
+
+def parse_languages(a_list):
+    """Return a list of distinct languages."""
+    a_set = set()
+
+    # parse text file
+    for item in a_list:
+        # split students and languages
+        student_lang = item.split(':')
+
+        # split languages
+        lang = student_lang[1].split(',')
+
+        # add languages to set
+        for l in lang:
+            if len(l.strip()) > 0:
+                a_set.add(l.strip())
+
+    # convert to list
+    b_list = []
+    for language in a_set:
+        b_list.append(language)
+
+    # sort list
+    b_list.sort()
+
+    return b_list
+
+
+path_students = '../../../Examples/Session01/students.txt'
+file_students = open(path_students, 'r')
+list_students = read_file_to_list(file_students)
+list_languages = parse_languages(list_students)