CS 1315 Final

syntax error

The program does not run, caught by the interpreter

runtime error

The program runs, but produces an error, caught by the interpreter

semantic error

The program runs, and does not produce an error, caught by the programmer. The program produces unexpected output

type conversion - int()

int, float, numeric str, True = 1, False = 0. Ex: can not convert int(“three”).

type conversion - float()

int, float, numeric str, True = 1.0, False = 0.0. Ex: can not convert float(“three”).

type conversion - str()

int, float, numeric str, str, True = “True”, False = “False”

type conversion - bool()

all data types = True except bool(False) and bool(0)

*

multiplication

/

division

//

floor division, a whole number

bigger number % smaller number

modulus, gives remainder after floor division

smaller number % bigger number

result is the smaller number

Order of Precedence

PEMDAS + R + L

print()

displays a value on the screen

input()

gets input from the user to assign to a variable

immutable

once created, object cannot be changed. If it is repeated, a new variable is assigned. EX: str

Operator: *

makes copies of operand. multiplication of numeric literals. repetition of a str literal by an integer

Operator: +

addition of numeric literals, concatenation of str literals

Operators: not (!), and (&), or (|)

• True and True is True, all others are False

• False or False is False, all others are True

• not False is True

• not True is False

\n

new line

\t

tab

\\

back slash

\’

single quote

\”

double quote

len()

The number of characters in a string is called the length of the string. Empty string (“ ”) has len() of 0. Each character in a string has an index value; 0 through len()-1

index[0]

first char

index[–1] or [len()-1]

last char

Operator: []

returns a char at a given string index, spaces count as chars

f-string

formatted string literal. Use {} to refer to variables. Ex: print(f “{name} your total is ${total:.2f}.”) → Bob your total is $5.40.

slicing [X:X:X]

• [start:stop:step] spaces count as chars so include them in the steps

• steps do not depend on index number, just number of chars

• Default start is index[0], default stop is index[-1], default step is 1

• last char is not included

string methods no arguments

string methods with arguments

Operator: in

tests for membership

while loop

condition-controlled

for loop

count-controlled

lists

• defined by []

• indexable

• mutable

list.remove(value)

Removes the first occurrence of a specified value

list.insert(index,value)

Adds an element at the specified index position

list.append(value)

sed to add items to a list – item is appended to the end of the existing list

del list[index]

removes an element from a list - can be used to delete a single index of a list, a slice of a list, or the complete list

list.insert(index,value)

inserts an element at the specified position

separator.join(iterable)

returns all items in an iterable and joins them into one string.

string.strip()

removes any set of characters that are leading or trailing a string

string.split()

returns a list of sub-strings from the string

break

used to break out of a for loop or a while loop

tuple

• a comma-separated sequence of values enclosed in parentheses.

• immutable

• EX: oneTup = (5,)

• can use + and * to add to tuple or multiply

packing

refers to tuples

unpacking

refers to tuples

tuple.index(value)

searches for a specified value and returns the first position if found

open txt: Reading mode

• retrieving data from an input file

• file_objectname = open(filename, 'r')

open txt: Writing mode

• saving data to an output file

• file_objectname = open(filename, 'w')

open txt: Appending mode

• adding data to an existing file, will create a file if the specified file does not exist

• file_objectname = open(filename, 'a')

open txt: Creating mode

• will create a file, returns an error if the file exist

• file_objectname = open(filename, 'x')

.read()

read all characters as a single str

used to read entire file contents as a str.

.readline()

returns one line from the file

used to read a line from the file as a str

.readlines()

Returns a list of strings, each representing a single line of the file

used to read each line as a str into a list.

.write()

used to write data to a file, will overwrite any existing data, and does not include a newline character

.close()

always close your files, as all changes are not written until after close.

txt files

A plain text file containing unformatted text

csv files

A comma-separated values file used for storing tabular data
•Each line represents a data record.
•Fields within the record are separated by commas.

csv.reader()

Reads rows from a CSV file

Converts each row into a list of strings

csv.writer()

writes rows to a CSV file

Writes iterable data (e.g., list/tuple) to a CSV file

{}

indicates a dictionary

how to index into a dictionary

use the key