Python Keywords, Concepts, Functions
See also Python Programming - Getting Started
Following are terse descriptions for Python3 keywords, programming concepts, and commonly used functions. For more information, see w3schools for a bit more explanation and python.org for the language reference.
The following are heavily used in all levels of Python programming. This is a minimum set of keywords to know how to use.
break- exit the current loop
continue- in a loop, go to next iteration of the loop
is- determine whether two objects are the same object (not just value)
import, from- to load a module
def- declare a function
while- loop with only condition
if, elif, else- conditional statements (three keywords)
for- loop with that iterates through a list
return- keyword to send a value back from a function
and- boolean operator, True only if both sides are True
or- boolean operator, True if either side is True
not- boolean operator, negates
True, False- boolean values (two keywords)
del- remove from a list by position
try, except- handle an exception, basic use (2 keywords)
raise, assert- raise/indicate an exception (2 keywords)
in- test if something is inside of a list/string/tuple/dictionary
None- special value for a variable that has no value
pass- empty statement that does not do anything
These keywords are often not introduced or heavily used until the second Python course.
as, finally, with, else- exception handling, more keywords (4 keywords)
class- defining new class data type (for object-oriented programming)
lambda- create unnamed / anonymous function
global, nonlocal- access variables outside of current scope (2 keywords)
async, await- for writing asynchronous code with asynchio package (2 keywords)
yield- for creating generator functions
See this video for a demo and explanation of basic data types and variables.
These are terms that we use to describe programs. These are terms that have a precise meaning when talking about programs.
- string - text data type
- boolean - data type for True and False
- floating point - data type that stores numbers with fractional parts (e.g., 3.14 or 2.2)
- integer - data type that stores only integers
None- a special value in Python that means "nothing" but is different than 0, False, and ""
- variable - name for a place in memory to store values. Two basic things you do with a variable - (i) store a value into the variable, (ii) get the value from the variable.
- keywords - also called reserved words - these are names that should not be used for variable names because they have special meaning to python. Example:
foris used for loops and shouldn't be used as a variable name.
- function - also called procedures or methods - name for a block of code that does something and that your code can use when needed. Two basic things you can do with a function - (i) define what the function is (specify the code for the function), (ii) call the function later on in your code. Three main parts of defining function - (a) function code (called the body), (b) function parameters (aka input variables), (c) function return values. Three main parts of calling/using a function - (1) specify the arguments to the function (which are passed in to the parameters of the function), (2) call the function, (3) get the return value of the function.
- flow chart - diagram that shows the steps / flow of control in a program (also used to diagram decision-making in other settings - e.g., diagnosis of an illness, managing a factory, ...)
- binary operator - operator that takes two values to produce a result. An example is addition, 2 + 3 results in 5. Another example is == comparison, 'hi' == 'bye' results in False because the two are not equal.
- unary operator - operator that takes one value to produce a result. An example is Boolean not, not True results in False.
- operator precedence - rules for which operators are evaluated first in an expression. For example, in 1 + 2 * 3, the multiplication is performed first, giving 1 + 6, and then the + is performed to result in 7. For Python, see python.org.
- operator associativity - rule whether operators of the same type are evaluated left-to-right or right-to-left. Math operators are left-to-right. For Python, see python.org.
Commonly Used Functions
int, float, str- functions to convert to integer, floating point number, or string
range- function to generate a sequence of numbers
len- function to get the length of a string, list, or tuple