Last Time (§§ 4,5)

There are three sequence types.

• lists: a mutable heterogeneous sequence type
• tuples: an immutable heterogeneous sequence type
• strings: an immutable sequence of characters

We also learned about the Python documentation and the builtin functions and types pages.

§§ 11-13 discuss pooling, aliasing and the "pointing relationship" that has been a theme in class. Reading these will clarify a lot for you.

Truthy, Falsy and None

An object is truthy if when it is cast to a boolean, the result is True.

An object is falsy if when it is cast to a boolean, the result is True.

None is Python's graveyard type. None is falsy.

Comments

print and its Many Powers (§ 8)

# what does this do?
# this is the comment token
# python ignores everything from it to the end of the line.
print("Hello")
print(1,2,3, True, "cows", [1,2,3])
print(1,2,3, True, "cows", [1,2,3], sep = " * ")
print(1,2,3, True, "cows", [1,2,3], sep = "|")
print(1,2,3, True, "cows", [1,2,3], end = "FOO")
print("a", end="")
print("b", end="")
print("a", end="")
print("c", end="")
print("d", end="")

The Symbol Table and Expressions (§ 9)

When you create a variable you write on the symbol table.

*
**
***
****
*****
******    

      *
     * *
    * * *
   * * * * 
  * * * * * 
 * * * * * * 
     * *
     * *