Elements of Python

Elements of Python

• Vocabulary/Words

  : Variables and Reserved words (Chapter 2)
  

• Sentence structure

  : Valid syntax patterns (Chapter 3-5)
  

• Story structure

  : Constructing a program for a purpose
  
  

Reserved Words

: You cannot use reserved words as variavle names / identifiers

False	class	return	is	finally
None	if	for	lambda	continue
True	def	from	while	nonlocal
and	del	global	not	with
as	elif	try	or	yield
assert	else	import	pass	print
break	except	in	raise

Python Scripts

• Interactive Python is good for experiments and programs of 3-4 lines long.
• Most programs are much longer, so we type them into a file and tell Python to run the commands in the file.
• In a sense, we are “givind Python a script”.
• As a convention, we add “.py” as the suffix on the end of these files to indicate they contain Python.
  
  

Program Steps or Program Flow

• Like a recipe or installation instructions, a program is a sequence of steps to be done in order.
• Some steps are conditional - they may be skipped. → If
  
• Sometimes a step or group of steps is to be repeated.
• Sometimes we store a set of steps to be used over and over as needed several places throughout the //Sprogram. (Chapter 4)

//Sequential 
name = input('Enter file:')
handle = open(name, 'r')

counts = dict()

//Repeated
for line in handle:
		words = line.split()
		for word in words:
				counts[word] = counts.get(word, 0) + 1
bigcount = None
bigword = None
for word.count in counts.items():
		//Conditional 
		if bigcount is None of count > bigcount:
				bigword = word
				bigcount = count
print(bigword, bigcount)

Summary

• This is a quick overview of Chapter 1
• We will revisit these concepts throughout the course
• Focus on the big picture