wk0.1 A curious case of conditionals

Intro to git and github

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Read these:

A few challenges

Complete reverse_string and primes challenges in challenge folder.

Reviewing some ideas from yesterday

# Example from yesterday def t(num): if 10 <= num < 15: print("hot") elif num > 15: print("hotter") else: print("cold") # What does this function do? for i in range(4): for j in range(10): if j % 3 == 0: continue if j > 7 and j % 2 == 0: break else: print('i equals', i) print('j equals', j) print('------------')



In [3]:

    
#a = [1,2,3]
#b = a
#b is a
#b == a
#b = a[:]



In [4]:

    
#b == a
#b = a[:]

While Conditional.: return discussion

Follow up on yesterday's discussion on conditionals

more on conditionals:

is and is not
- difference between is and ==



In [55]:

    
4 is 2**2









    Out[55]:





True

Try evaluating each of the lines below in your python REPL. What's going on?

a = [1, 2, 3]
b = a
b is a
b == a
b = a[:]
b is a
b == a

If you have a hypothesis about the difference between is and ==, devise some tests you could try out to disprove your hypothesis. Implement them. Were you correct?

in and not in



In [63]:

    
# a in range(10)

assert a == 1
30 in range(10)









    



---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-63-5814fa79f306> in <module>()
      1 # a in range(10)
      2 
----> 3 assert a == 1
      4 30 in range(10)

AssertionError:

and, or



In [83]:

    
x = False
y = 0

x/y and x









    



---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-83-4bd792ffccf8> in <module>()
      2 y = 0
      3 
----> 4 x/y and x

ZeroDivisionError: division by zero

comparison priority

not has the highest priority and or the lowest, so that A and not B or C is equivalent to (A and (not B)) or C.
Short circuit operators



In [9]:

    
#1000 == 10**3









    Out[9]:





True



In [10]:

    
#1000 is 10**3









    Out[10]:





False



In [12]:

    
#4 is 2**2
#python stores small values,  whereas with 10**3 it has to calculate









    Out[12]:





True



In [20]:

    
#a = [1,2,3]
#c =[1,2,3]
#b =a
#a is c









    Out[20]:





False



In [21]:

    
#a[:] is not b









    Out[21]:





True



In [32]:

    
#for x in range(10):
#    print (x)



In [33]:

    
#10 <= x and x < 20









    Out[33]:





False



In [36]:

    
#x = 1.5
#if x < 10 and x > 0:
#    print ("x is between ten and zero")









    



x is between ten and zero



In [37]:

    
#x = 'a'
#if x == 'a' or x =='b':
#    print('x is a or b')









    



x is a or b



In [41]:

    
#'a' or 'b'









    Out[41]:





'a'



In [42]:

    
2 or 3









    Out[42]:





2



In [43]:

    
'''x = True
y = True

not (x and y)'''









    Out[43]:





False



In [46]:

    
'''x = False
y = 0
x and x/y
#and requires both to be true so the error of the division by zero is superceded by the falsity of the first condition''''









    Out[46]:





False

More string and list practice

Add elements from a list L to the end of another list at least three different ways.



In [90]:

    
a = [1, 2, 3]
L = [4, 5, 6]

a[len(a):]









    Out[90]:





[]

Insert elements into a list at least two different ways.



In [96]:

    
a[:4] + ['b'] + a[4:]









    Out[96]:





['a', 6, 6, 1, 'b', 'a', 2, 3]

Insert an element into a string (this might take more than one step...).



In [105]:

    
str1 = "hello"
str1 = list(str1)
str1.insert(3, 'demo')
str1 = ''.join(str1)
str1

# str1 = "Hello world"
# str1 = str1[:3] + 'llllll' + str1[4:]
# str1









    Out[105]:





'heldemolo'

Remove an item from a list by value.



In [110]:

    
lst  = [1 , 2, 3, 4]
lst.remove(3)
lst









    Out[110]:





[1, 2, 4]

Remove an item from a list by index.



In [114]:

    
lst.pop(0)
lst









    Out[114]:





[4]

Remove all items from a list two different ways.



In [121]:

    
lst = [1, 2, 3, 4]

lst.clear()
lst









    Out[121]:





[]

Return the index in the list of the first item whose value is x.



In [123]:

    
lst = [1, 2, 2, 3, 4]
lst.index(2)









    Out[123]:





1

Return the number of times x appears in the list.



In [126]:

    
lst.count(1)









    Out[126]:





1

Capitalize the first element in a string



In [143]:

    
lst = [1, 2, 3]
lst.append(5)

lst









    Out[143]:





[1, 2, 3, 5]



In [146]:

    
str1 ='abc'
b = list(str1).append(5)
b









    Out[146]:





['a', 'b', 'c', 5]

Capitalize all elements in a string



In [166]:

    
def %(duh):
    """ Append 5 to the end of the list"""
    return duh + '5'









    



  File "<ipython-input-166-ebe37b1dcb76>", line 1
    def %(duh):
        ^
SyntaxError: invalid syntax



In [ ]:

    
def area(xadsf787adf, asdfjljk4):
    return xadsf787adf*asdfjljk4



In [164]:

    
foo = 7
bar = 10
area(foo, bar)









    Out[164]:





70



In [152]:

    
str1 = 'asdf'
#string_changer(str1)









    Out[152]:





'asdf5'

Strip leading, trailing, and all whitespace (ex. leading: ' asdf ' --> 'asdf ', trailing:' asdf ' --> ' asdf', all:' asdf ' --> 'asdf').



In [188]:

    
def namer(n, a):
    print('My name is {name} and my age is {age}'.format(age=a, name=n))
    
namer('Richie', 8)









    



My name is Richie and my age is 8



In [ ]:

    
str1.split()

Split a sentence into a list of words (no whitespace), how would you split on comma or semi-colon?
Read up on how to format strings



In [119]:

    
#0.
a = ['x',2,3]
b = [4,5,6]
f = a.pop()
b.append(f)
g = a.pop()
b.append(g)
h = a.pop()
b.append(h)
b


w = [1,2,3]
w.insert(3,4)
w









    Out[119]:





[1, 2, 3, 4]



In [125]:

    
'Hello my name is Nick'.split()









    Out[125]:





['Hello', 'my', 'name', 'is', 'Nick']



In [ ]:



In [97]:

    
a.index('x')









    Out[97]:





0



In [99]:

    
a.count('x')









    Out[99]:





1



In [103]:

    
'hello'.capitalize()









    Out[103]:





'Hello'



In [106]:

    
'hello'.upper()









    Out[106]:





'HELLO'



In [130]:

    
a = [1,2,3]
L = [4,5,6]
a.extend(L)
a









    Out[130]:





[1, 2, 3, 4, 5, 6]



In [133]:

    
a=[1,2,3]
L = [4,5,6]
a + L









    Out[133]:





[1, 2, 3, 4, 5, 6]



In [138]:

    
a = [1,2,3]
L = [4,5,6]
for x in a:
    L.append(x)
print (L)









    



[4, 5, 6, 1, 2, 3]



In [141]:

    
a = [1,2,3]
a.append(4)
a









    Out[141]:





[1, 2, 3, 4]



In [143]:

    
a.insert(4,5)
a









    Out[143]:





[1, 2, 3, 4, 5, 5]



In [149]:

    
#insert element into a string
str1 = 'hello'
str1 = list(str1)
str1.insert(3,'b')
str1 = ''.join(str1)
str1

str1 = 'hello world'
str1 = str1[:3] + 'llll' + str1[4:]
str1









    Out[149]:





'helllllo world'



In [150]:

    
#remove an item by value
lst = [1,2,3]
lst.remove(3)
lst









    Out[150]:





[1, 2]



In [151]:

    
#remove an item by index
lst.pop(0)
lst









    Out[151]:





[2]



In [153]:

    
# remove all items from a list two different ways
lst = [1,2,3,4]
del lst[:]
lst

lst = [1,2,3,4]
lst.clear()
lst









    Out[153]:





[]



In [ ]:

    
#Return the index in the list of the first item whose value is x



In [155]:

    
str1 = 'abc'
b = list(str1).append(5)
b
#immutable always outputs something, mutable does not



In [156]:

    
def string_changer(duh):
    return duh + '5'



In [157]:

    
str1 = 'asdf'
string_changer(str1)









    Out[157]:





'asdf5'



In [158]:

    
def area(w,h):
    return w*h



In [159]:

    
area(3,4)









    Out[159]:





12



In [161]:

    
#strip leading, trailing and all whitespace

#lstrip,rstrip,strip

str1 = '          absad          '
str1.strip()









    Out[161]:





'asd   sad'



In [168]:

    
str1 = '   asd  fw'
b = str1.split()
''.join(b)









    Out[168]:





'asdfw'



In [171]:

    
def namer(name):
    print ('My name is {}'.format(name))

namer('Joe')









    



My name is Joe



In [172]:

    
def namer(n):
    print ('My name is {name}'.format(name=n))

namer('Joe')









    



My name is Joe



In [ ]:

    
#Split a sentence 

str1.split(sep=None)



In [176]:

Intro to pins assignment

Intro to try/except and error handling
- Syntax errors vs. exceptions



In [7]:

    
10 * (1/0)









    



---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-7-9ce172bd90a7> in <module>()
----> 1 10 * (1/0)

ZeroDivisionError: division by zero



In [6]:

    
4 + spam*3









    



---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-6-6b1dfe582d2e> in <module>()
----> 1 4 + spam*3

NameError: name 'spam' is not defined



In [ ]:

    
'2' + 2

Handing exceptions



In [ ]:

    
while True:
    try:
        x = int(input("Please enter a number: "))
        break
    except ValueError:
        print("Oops!  That was no valid number.  Try again...")



In [5]:

    
b == a
b = a[:]



In [ ]:



In [ ]: