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('------------')

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

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

Intro to pins assignment

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



In [ ]:

    
10 * (1/0)



In [ ]:

    
4 + spam*3



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...")