Zelle - Chapter 11.pdf - CTools

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What does x = list() mean? • These are called “constructors” - they make an empty list, str, or dictionary • We can make an “fully formed empty” object and then add data to it using capabilities (aka methods) >>> a = list() >>> print a [] >>> print type(a) >>> b = dict() >>> print b {} >>> print type(b) >>> a.append("fred") >>> print a ['fred'] >>> c = str() >>> d = int() >>> print d 0
Object Oriented Summary • Variables (Objects) contain data and capabilities • The dir() function asks Python to list capabilities • We call object capabilities “methods” • We can construct fresh, empty objects using constructors like list() • Everything in Python (even constants) are objects
Page 1 and 2: Data Collections Zelle - Chapter 11
Page 3 and 4: What is a Collection? • A collect
Page 5 and 6: Terminology: Object • An Object i
Page 7 and 8: The Python List Object
Page 9 and 10: print grades [100, 97, 100] >>> new
Page 11 and 12: Why lists start at zero? • Initia
Page 13 and 14: lst = [ 21, 14, 4, 3, 12, 18] >>> p
Page 15 and 16: Quick Peek: Object Oriented
Page 17 and 18: One way to find out Capabilities Bu
Page 19: Try dir() with a String >>> y = “
Page 23 and 24: Dictionaries • Dictionaries are P
Page 25 and 26: purse = dict() >>> purse['money'] =
Page 27 and 28: lst = list() >>> lst.append(21) >>>
Page 29 and 30: Dictionary Literals (Constants) •
Page 31 and 32: Dictionary Patterns • It is an er
Page 33 and 34: Dictionary Counting • Since it is
Page 35 and 36: Retrieving lists of Keys and Values
Page 37 and 38: Dictionary Maximum Loop $ cat dictm
Page 39 and 40: Dictionaries are not Ordered >>> dc
Page 41 and 42: Counting Words python wordcount.py
Page 43 and 44: Summary: Two Collections • List

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