Module 2 - Anatomy of a Python Statement Flashcards
what can python statements do?
Creating data objects
Giving names to data objects
Performing operations on data objects
Use properties of data objects to execute other statements conditionally and/or repeatedly
yypes of python statements
simple statements and compound statements.
simple statement.
one line of code
compound statements.
contain multiple commands or instructions that are dependent on each other in some ways
tokenization
breaking up the statement into so-called tokens.
Tokens
smallest meaningful unit in a Python program. composed of sequences of characters
types of tokens
- Keywords
- Identifiers
- Literals
- Delimiters
- Operators
- Whitespace Tokens
character
alphabet, a number, a punctuation or a symbol like +, *, &, ^, etc.
Keywords
words reserved for a specific purpose
Identifiers
used to refer to objects in memory
features of an identifier
begins w letter or underscore
optionally, continues w letter, digit, or underscore
cannot be a python keyword
is python case-sensitive?
yes. uppercase and lowercase letters are considered different characters.
Literals
used to represent constant, fixed values in your program
types of literals
integer literals
floating point literals
string literals
integer literals
Integer literals are tokens made up of one or more digits and no other characters.
floating point literals
tokens used to represent a real number.
A float literal contains a dot (.) and one or more digits.
string literals
String literals are sequences of characters surrounded by single quotation marks (‘) or double quotation marks (“)
Delimiters
special characters whose functions vary depending on context.
Operators
tokens that perform operations on objects
Whitespace Tokens
three individual Python tokens that do not belong to any token kind.
indent
dedent
newline
parsing
the process of python understanding the program
how does python parse out tokens?
Python reads statements left-to-right and top-to-bottom
Python looks for the longest continuous sequence of tokens possible that can be read as a statement
Whitespace can be used to manually separate tokens
indentation rules
if you indent once, and the next line has the same indentation level, only one indent token will be parsed, the first one
a single line of code can only have one indent token at a time.
a single line of code can have multiple dedent tokens
features of an object
identity, type, value
what is the identity of an object? how can you find it?
refers to the location where it is stored in the computer memory.
You can find the identity of an object by using the id function.
what is the type of an object? how can you find it?
determines the kinds of operations that are performed on it and how it can be stored in memory.
You can find the type of an object by using the type function.
what is the value of an object
The value of an object determines the memory contents for each particular object of a certain type.
can Two distinct objects have the same type, value, and identity?
Two distinct objects can have the same type and the same value—but they will always have different identities.
list vs tuple
while tuples are immutable objects, lists are mutable (can be changed)
lists are square brackets.
types of simple statements
assignment statement
expression statement
import statement
assignment statement
allow us to give names to objects in memory
expression statement
piece of code that can be evaluated to produce a value
import statement
allows us to gain access to different modules with specific functionalities
Types of expression statements
atomic expression
attribute reference
subscription operation
unary + binary
slicing
function call
atomic expression
a piece of code that has a value and cannot be broken down into smaller pieces.
> > > 42
> > > x = 1
x
> > > [1,2,3]
Function Calls
represent computations or operations on objects that are commonly used in programs. Rather than writing the same lines of code repeatedly for a single computation, we can call the function that does it all for us in one line.
ex: print
Subscription Operations
used to select an element from a list, string, or tuple.
This is achieved by specifying the index or position of the item within a sequence. We always start counting from 0.
> > > “Hello World!”[0]
‘H’
Slicing
Slicing allows us to select a range of items or characters from a sequence, such as a string, list, or tuple.
> > > “catfish”[0:3]
‘cat’
> > > “catfish”[0:3]
‘cat’
why does it return ‘cat’ and not ‘catf’?
0 does refer to the first item in the sequence
Attribute Reference
Some objects in Python have so-called attributes. This can be seen in modules. Modules may contain functions and constants, which are considered attributes of that specific module.
