Term
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Definition
| The process of saving data in a file; it is copied from a variable in RAM to the file. |
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Term
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Definition
| A file that data is written to |
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Term
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Definition
| The process of retrieving data from a file; data is copied from the file to RAM, referenced by variables. |
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Term
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Definition
| A file from which the data is read |
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Term
| Three steps when a program uses a file |
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Definition
| 1. Open the file 2. Process the file 3. Close the file |
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Term
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Definition
| Contains data that has been encoded as text; can be opened and viewed in Notepad |
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Term
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Definition
| Contains data that has not been converted to text; intended only for a program to read |
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Term
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Definition
| File is read sequentially from beginning to end; can't skip to desired data |
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Term
| Direct access file aka Random access file |
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Definition
| Can jump directly to any piece of data in the file without having to read data that comes before it |
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Term
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Definition
| Short sequences of characters that appear at the end of a filename preceded by a period; extension indicates type of data stored in the file |
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Term
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Definition
Object associated with a specific file
Provides a way for a program to work with the file; file object referenced by a variable |
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Term
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Definition
Used to open a file; creates a file object and associates it with a file on the disk
General format:
file_object = open(filename, mode) |
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Term
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Definition
| String specifying how the file will be opened: reading only ('r'), writing ('w')- writes over file if already exists, and appending ('a’) - appends data to the end of the file if it already exists |
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Term
| Specifying location of file |
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Definition
| Open function assumes file is in the same directory as the program; can specify alternative path using the letter 'r' before the filename |
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Term
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Definition
| A function that belongs to an object and performs some operation using that object; file object’s write method used to write data to the file: file_variable.write(string) |
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Term
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Definition
| File object method that reads entire file contents into memory; ignores \n when printing |
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Term
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Definition
| File object method that reads a line from the file, one at a time; terminated with \n and line is returned as a string, including '\n', printing an extra line between each read line |
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Term
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Definition
| Marks the location of the next item to be read from a file; the read position of the file updates after every call to readline() |
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Term
| Concatenating newline to a string |
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Definition
| Most data items written to a file are values referenced by variables; usually necessary to concatenate a '\n' to data before writing it using a + operator |
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Term
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Definition
In many cases need to remove '\n' from string after it is read from a file; string method that strips specific characters from end of the string:
line1 = infile.rstrip('\n') |
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Term
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Definition
| Numbers must be converted to a string before written to a file; must be converted back to int or float when reading file in order to perform operations |
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Term
| While loop to process files |
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Definition
| Often the number of items stored in file is unknown; the readline method uses an empty string as a sentinel when end of file is reached: while line != '' |
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Term
| For loop to process files |
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Definition
A priming read is not necessary and automatically stops when end of file is reached: for line in file_object:
statements |
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Term
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Definition
| A complete set of data that describes one item; used with sequential access file |
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Term
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Definition
| A single piece of data within a record |
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Term
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Definition
| An error that occurs while a program is running, causing the program to abruptly halt |
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Term
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Definition
| Error message that gives information regarding line numbers that caused the exception; indicates the type of exception and brief description of the error that caused exception to be raised |
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Term
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Definition
code that responds when exceptions are raised and prevents program from crashing:
try:
statements
except exceptionName:
statements
An except clause that doesn't specify the exception will handle any exception raised or else need to write except clause for each type of exception that needs to be handled |
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Term
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Definition
| Statements that can potentially raise an exception |
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Term
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Definition
| statements contained in except block |
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Term
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Definition
Created in memory when an exception is thrown; contains a default message pertaining to the exception
Ex: except ValueError as err:
Can pass exception object variable (err- which is not a special name) to print function to display the default error message |
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Term
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Definition
| Try/except statement may include an optional else clause, which appears after all the except clauses |
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Term
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Definition
| Block of statements executed after statements in try suite, only if no exceptions were raised; if exception was raised, the else suite is skipped |
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Term
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Definition
| Block of statements after the finally clause; execute whether an exception occurs or not; purpose is to perform cleanup before exiting |
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Term
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Definition
| An object that holds multiple items of data, stored one after the other; two main types: lists and tuples |
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Term
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Definition
An object that contains multiple data items; they are mutable, meaning their contents can be changed during a program's execution; and they're dynamic, meaning that items can be added or removed:
list = [item1, item2, etc.] |
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Term
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Definition
| An item in a list; can be different data types |
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Term
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Definition
Makes multiple copies of a list and joins them together; the * symbol is a repetition operator when applied to a sequence and an integer:
list * n
applies to strings as well |
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Term
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Definition
A number specifying the position of an element in a list; enables access to individual element in list;
index of first element in the list is 0, second element is 1, and n’th element is n-1 |
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Term
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Definition
| Raised if an invalid index is used |
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Term
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Definition
| Returns the length of a sequence such as a list |
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Term
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Definition
| The + operator can be used to concatenate two lists; can only concatenate a list with another list |
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Term
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Definition
| A span of items that are taken from a sequence; list slicing format: list[start : end]; span is a list containing copies of elements from start up to, but not including, end; if start not specified, 0 is used for start index and if end not specified, len(list) is used for end index |
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Term
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Definition
| Format: item in (or not in) list; returns either True or False |
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Term
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Definition
| Used to add items to a list – item is appended to the end of the existing list: list.append(item) |
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Term
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Definition
| Used to determine where an item is located in a list; returns the index of the first element in the list containing item; raises ValueError exception if item not in the list |
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Term
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Definition
| Used to insert item at position index in the list |
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Term
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Definition
| Used to sort the elements of the list in ascending order; can be used for letters and words; list.sort() |
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Term
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Definition
| Removes the first occurrence of item in the list |
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Term
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Definition
| Reverses the order of the elements in the list |
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Term
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Definition
| Removes an element from a specific index in a list: del list[i]; different from remove() because remove requires you to tell it the specific element to remove if it exists in the list (ex: remove(‘Pizza’)) but del will delete the item at index i regardless of what that item is |
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Term
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Definition
| Built-in functions that returns the item that has the lowest or highest value in a sequence |
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Term
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Definition
To make a copy of a list you must copy each element of the list; two methods to do this:
creating a new empty list and using a for loop to add a copy of each element from the original list to the new list or
creating a new empty list and concatenating the old list to the new empty list |
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Term
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Definition
| Writes a list to a file; does not automatically write \n at then end of each item; use a for loop to write each element and \n |
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Term
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Definition
| Returns a file's contents as a list of strings |
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Term
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Definition
| A list that contains other lists as its elements; also known as nested list; common to think of two-dimensional lists as having rows and columns; useful for working with multiple sets of data; to process data in a two-dimensional list need to use two indexes |
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Term
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Definition
An immutable sequence that is very similar to a list
but once it is created it cannot be changed; do not support the methods:
append
remove
insert
reverse
sort |
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Term
| List() and Tuple() functions |
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Definition
| Used to convert a list to tuple and vice versa |
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Term
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Definition
| Strings are also sequences; use a for loop to access individual characters of a string; can also access individual characters using indexing |
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Term
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Definition
| Appending one string to the end of another string; done with += or + operator; does not include space |
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Term
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Definition
| Span of items taken from a sequence, known as substring: string[start : end] |
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Term
| String in and not in operator |
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Definition
Used to determine if a string is (or not) contained in another string: string1 in string2,
string1 and string2 can be string literals or variables referencing strings |
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Term
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Definition
Test a string for specific characteristics; generally Boolean methods, that return True if a condition exists, and False otherwise:
string.isalpha()
isalnum()
isdigit()
etc. |
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Term
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Definition
Return modified versions of strings simulating strings as mutable objects; for example, string comparisons are case sensitive; can use:
lower()
upper()
etc. |
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Term
| Searching and replacing methods |
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Definition
| Searches for substrings and/or replaces occurrences of a substring with another string |
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Term
| endswith(substring) method |
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Definition
| Checks if the string ends with substring; returns True or False |
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Term
| startswith(substring) method |
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Definition
| Checks if the string starts with substring; returns True or False |
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Term
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Definition
| Searches for substring within the string; returns lowest index of the substring, or if the substring is not contained in the string, returns -1 |
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Term
| replace(substring, new_string) method |
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Definition
| Returns a copy of the string where every occurrence of substring is replaced with new_string |
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Term
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Definition
| Returns a list containing the words in the string; by default, uses space as separator but can specify a different separator by passing it as an argument to the split method: string.split('/') |
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Term
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Definition
Object that stores a collection of data; each element consists of a key and a value and is often referred to as mapping of key to value; key must be an immutable object (such as a string):
dictionary = {key1:val1, key2:val2} |
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Term
| Retrieving a value from a dictionary |
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Definition
| General format: dictionary[key]; if key in the dictionary, associated value is returned, otherwise, KeyError exception is raised; can use in or not in operator to prevent KeyError exception |
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Term
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Definition
| dictionary[key] = value; will replace old value if key already exists |
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Term
| Deleting a key-value pair |
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Definition
| del dictionary[key]; if key not in dictionary, KeyError exception raised |
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Term
| Creating an empty dictionary |
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Definition
| dictionary = {} or dictionary = dict() |
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Term
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Definition
| Iterates over all the keys of the dictionary |
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Term
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Definition
| Deletes all the elements in a dictionary, leaving it empty: dictionary.clear() |
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Term
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Definition
| Gets a value associated with specified key from the dictionary: dictionary.get(key, default); default is returned if key is not found |
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Term
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Definition
| Returns all the dictionaries keys and associated values: dictionary.items(); returned as a dictionary view where each element in dictionary view is a tuple which contains a key and its associated value |
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Term
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Definition
| Returns all the dictionaries keys as a sequence |
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Term
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Definition
| Returns value associated with specified key and removes that key-value pair from the dictionary: dictionary.pop(key, default); default is returned if key is not found |
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Term
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Definition
| Returns a randomly selected key-value pair and removes that key-value pair from the dictionary; can use a multiple assignment where multiple variables are assigned at once: k, v = dictionary.popitem(), which returns a tuple |
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Term
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Definition
| Returns all the dictionary's values as a sequence (list) |
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Term
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Definition
| Object that stores a collection of data in same way as mathematical set |
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Term
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Definition
Used to create a set - for empty set, call set()
; for non-empty set, call set(argument) where argument is an object that contains iterable elements i.e. list, tuple, string (if argument is a string, each character becomes a set element) |
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Term
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Definition
Adds an element to a set: myset = set()
myset.add(1) |
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Term
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Definition
| Adds a group of elements to a set; argument must be a sequence containing iterable elements, and each of the elements is added to the set |
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Term
| Remove and discard methods |
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Definition
Remove the specified item from the set; the item that should be removed can be passed to either method as an argument, the only difference between remove and discard is how they behave when the specified item is not found in the set:
remove method raises a KeyError exception;
discard method does not raise an exception |
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Term
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Definition
| Clears all the elements of the set |
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Term
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Definition
Format: for item in set:
-set is an unordered structure so print out may be in different order than the initial set |
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Term
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Definition
A set that contains all the elements of both sets; to find the union of two sets: set1.union(set2)
or set1 | set2 |
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Term
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Definition
| A set that contains only the elements found in both sets; to find the intersection of two sets: set1.intersection(set2) or set1 & set2 |
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Term
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Definition
| A set that contains the elements that appear in the first set but do not appear in the second set; to find the difference of two sets: set1.difference(set2) or set1 - set2 |
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Term
| Symmetric difference of two sets |
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Definition
| A set that contains the elements that are not shared by the two sets; to find the symmetric difference of two sets: set1.symmetric_difference(set2) or set1 ^ set2 |
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Term
| Issubset and issuperset methods |
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Definition
Subset: setA.issubset(setB) or setA <= setB
superset: setA.issuperset(setB) or setA >= setB |
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Term
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Definition
| Convert an object to a stream of bytes that can easily be stored in a file |
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Term
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Definition
Serializing an object:
-Import the pickle module
-Open a file for binary writing:
outfile = open('file.dat', 'wb')
-Call the pickle.dump function
pickle.dump(object, file)
-Close the file |
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Term
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Definition
-Import the pickle module
-Open a file for binary writing:
outfile = open('file.dat', 'rb')
-Call the pickle.load function
pickle.load(object, file)
-Close the file |
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Term
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Definition
| Writing programs made of functions that perform specific tasks; most of the programs we've worked with thus far |
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Term
| Object-oriented programming |
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Definition
| Centered on creating objects |
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Term
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Definition
| Entity that contains data and procedures; data contained in the object is known as data attributes (variables that reference data) and procedures that an object performs are known as methods - methods perform operations on the data attributes |
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Term
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Definition
| Combining data and code into a single object |
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Term
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Definition
| Object’s data attributes are hidden from code outside the object |
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Term
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Definition
| The same object can be used in different programs |
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Term
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Definition
| Define the state of an object: clock has seconds, minutes, and hours |
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Term
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Definition
| Allow external code to manipulate the object: setting an alarm |
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Term
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Definition
| Used for object’s inner workings: incrementing seconds on clock |
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Term
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Definition
| Code that specifies the data attributes and methods of a particular type of object |
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Term
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Definition
| An object created from a class |
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Term
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Definition
| Set of statements that define a class’s methods and data attributes: class Class_name: |
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Term
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Definition
| Required in every method in the class – references the specific object that the method is working on: |
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Term
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Definition
Automatically executed when an instance of the class is created; initializes object’s data attributes and assigns self parameter to the object that was just created:
def __init__ (self): |
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Term
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Definition
| The values of the object’s attribute at a given moment |
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Term
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Definition
| Displays the object’s state; automatically called when the object is passed as an argument to the print function or when the object is passed as an argument to the str function |
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Term
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Definition
| Belongs to a specific instance of a class; created when a method uses the self parameter to create an attribute |
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Term
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Definition
| Return a value from a class’s attribute without changing it; safe way for code outside the class to retrieve the value of attributes; method usually starts with the word Get and are therefore sometimes called getters |
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Term
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Definition
| Store or change the value of a data attribute; method usually starts with the word Set and are therefore sometimes called setters |
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Term
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Definition
Standard diagrams for graphically depicting object-oriented systems- general layout: box divided into three sections:
Top section: name of the class
Middle section: list of data attributes
Bottom section: list of class methods
Show inheritance by drawing a line with an open arrowhead from subclass to superclass |
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Term
| Identifying classes in a problem |
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Definition
1) Get written description of the problem domain - domain is the context of the problem
2) Identify all nouns in the description, each of which is a potential class
3)Refine the list to include only classes that are relevant to the problem |
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Term
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Definition
| Exists when one object is a specialized version of another object; specialized object has all the characteristics of the general object plus unique characteristics |
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Term
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Definition
Used to create an “is a” relationship between classes; the new class inherits the members of the class it extends
Ex: class Car(Automobile):
The initializer method of a subclass calls the initializer method of the superclass and then initializes the unique data attributes and adds method definitions for unique methods |
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Term
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Definition
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Term
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Definition
| A specialized class; essentially an extended version of the superclass; inherits attributes and methods of the superclass while new attributes and methods can be added |
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Term
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Definition
| An object’s ability to take different forms; allows subclasses to have methods with the same names as methods in their superclasses; it gives the ability for a program to call the correct method depending on the type of object that is used to call it |
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Term
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Definition
| Raised when a method receives an object which is not an instance of the right class |
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Term
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Definition
| Determines whether object is an instance of a class |
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Term
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Definition
| A function that calls itself |
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Term
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Definition
| The number of times a function calls itself |
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Term
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Definition
| When a function directly calls itself |
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Term
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Definition
| When function A calls function B, which in turn calls function A |
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