Python Collections

by D@CC
on 2024HAug20

Python has four types of Collections

For any questions refer to W3 School Pyton on the web.




Tuple

A Tuple is ORDERED and UNCHANGEABLE and allow duplicates
Items can be any data type
Multiple items in a single tuple can be many different data types.
A Tuple is written with round brackets "(" and ")"

eg  fruits

fruits = ("apple", "banana", "cherry")

Tuple items are indexed.  The first item has index [0], next has index [1] etc

A negative index number starts from the end -1 is the last






List

A List is a Tuple that can be changed.
A List is written with square brackets ("[" and "]")

Items added to a list are placed at the end of the list.





Set
is a collection which is UNORDERED, UNCHANGEABLE*, and unindexed. No duplicate members.

*Set items are unchangeable, but you can remove and/or add items whenever you like.

Set items cannot be identified by an index number

Sets are written with curly brackets

Sets cannot be referred to by index or key

Rules for Sets are the same as in set theory

True and 1 are considered the SAME value in a set.

If a Set is defined to include duplicate values, the duplicate values are not retained.





Dictionary
 is a collection which is ordered** and changeable. No duplicate members.

A Dictionary is written with curly brackets
Each dictionary contains key:value pairs

Duplicate values will overwrite existing values.

**As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered.

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print thisdict["brand"]
 will print
 "Ford"

thisdictionaryIndex = {
  "000":"Cole",
  "001":"Marcoux",
  "003":"Smith"
  "001":"Anderson",
}
print thisDictionaryIndex["000"]
  will print
 "Cole"
What will be printed by 
print thisDictionaryIndex["001"]
 or
print thisDictionaryIndex
 or
print thisDictionaryIndex[1]

Dictionaries are often used to house a complete index.
Two duplicate pairs are NOT retained,
  but two duplicate keys can occur.

EXERCISES

Exercise 01
Read in a serial data file containing records with an index.
Each record is of the format 00001,string\n
the two fields are separated by a comma
the first field is a 5 digit decimal number padded with zeroes in front
store the file in a Python dictionary name Dict
store the first field as a 5 digit string
store the second field as a string of characters, that may be null
The last record is empty containing only a "\n" line feed
Once the file has been read, print out the Python dictionary: Dict
Then print out the indexed entried in the Python dictionary
    for i in len(Dict)
        print(Dict[i])
    #for end

Store each record of the data file  as a pair in a Python dictionary.
Exercise 02
Try with a file with 2 duplicate records

Exercise 03
Try with a file with records that are not ordered by the key

Exercise 04
Try with a file with duplicate keys and different strings

Exercise 05
Try with a file with different keys and duplicate strings.

Exercise 06
 Load the preceding file into a Set (by ignoring the "key" field)

Exercise 07
 Load the precedinf file into a List  (by ignoring the "key" field)

Exercise 08
Add error checking to ensure that the serial file:
 is not devoid of any records  (ie empty)
 has at least one comma in every record
 every key is 5 digits long
 a comma exists in every column 6
 does not contain a null record (just a "\n")
 the file exists in the current directory
 does not contain a record longer than 87 characters
      (not including the line feed)
 file does not contain more than 5 records.
 has no keys that are not in ascending order
 has no strings that are not in ascending order
 has no non-digits in a key
 has no strings that are not 80 characters long
  

Exercise 09
For each type of collection
 load items "apple", "orange", "banana"
    for i in len(Coll)
        print(Coll[i])
    #for end

Exercise 10
Load a Tuple into a List then print it out
Load a Tuple into a Set, then print it out
Load a Tuple into a Dictionary with keys starting with 0 etc, then print it out

Exercis 11
Add an item to an existing List, then print
Add an item to an existing Set, then print
Add an item pair to an existing Dictionary, then print
Try to add an item to an existing Tuple, then print



/Python_Collections.txt