A VERY Brief Python Tutorial for EECS 486

The aim of this tutorial is to let students quickly get familiar with Python for EECS 486 course works. Kite is suggested.

Projects are handgraded so PLEASE comment your code

Basics

a = 7
a += 2 # a = a + 2
a -= 2 # a = a - 2
a *= 2 # a = a * 2
a **= 2 # a = a ** 2

text = "    Here is Playground.     "
text = text.strip() # "Here is Playground."
text = text.lower() # "here is playground."
text = text.upper() # "HERE IS PLAYGROUND."
text = text.replace('.', '!') # "HERE IS PLAYGROUND!"
text[0] = 'A' # Doesn't work, strings are immutable
tokens = text.split()
# ['HERE', 'IS', 'PLAYGROUND!']

text += "!@#$%^"  # "HERE IS PLAYGROUND!!@#$%^"

b = True
c = False
print(b and c) #False
print(b or c) #True
print(not b) #False

List

l = ['I', 'have', 'an', 'apple']
print(l[1]) # 'have'
print(l[-1]) # 'apple'
print(l[1:3]) # ['have', 'an']
print(l[1:]) # ['have', 'an', 'apple']
print(l[:-1]) # ['I', 'have', 'an']

len(l) # 4
l.append('pineapple')
l.append(1)
print(l) # ['I', 'have', 'an', 'apple', 'pineapple', 1]
x = l.pop()
print(x) # 1

print(l + tokens) 
# ['I', 'have', 'an', 'apple', 'pineapple', 'HERE', 'IS', 'PLAYGROUND!']
# l.extend(tokens)

# List assignment is by REFERENCE
array = ["an","bert","cindy","dirk"]
copyarray = array # creates a new reference “copyarray”
copyarray[2] = "ZZZ" # changes BOTH array as well as copyarray

# Any and All
any(x > 0 for x in [-5, -2, 0, 1])  # returns True     
any(x > 0 for x in [-15, -12, -20, -31])  # returns False

all(x < 0 for x in [-5, -2, 0, 1])  # returns False     
all(x < 0 for x in [-15, -12, -20, -31])  # returns True

#filter(lambda x: CONDITION, LIST)    
# returns a list of all items from list that satisfy some condition.
filter(lambda x: x > 10, [1,2,4,8,16,25]) 
# [16,25]   

# map (OPERATION, LIST)  
# perform an arbitrary operation on each element of a list.
map(lambda x: x*2, [1,2,4,8,16,25])  
# [2, 4, 8, 16, 32, 50]

Loop

for x in l:
	print(x)

for a in range(3):
	print(a)

for i in range(len(l)):
	print(l[i])

for i, x in enumerate(l):
	print("#" + str(i) + ":")
	print(x)

i = 0
while(i < len(l)):
	print(l[i])
	i += 1

List Comprehension

squares = [x ** 2 for x in range(10)]
# [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
even_squares = [x ** 2 for x in range(10) if x % 2 == 0]
# [0, 4, 16, 36, 64]

Dict

m = {}
for i, x in enumerate(l):
	m[i] = x
# {0: 'I', 1: 'have', 2: 'an', 3: 'apple', 4: 'pineapple', 5: 'HERE', 6: 'IS', 7: 'PLAYGROUND!'}
del m[0]
# {1: 'have', 2: 'an', 3: 'apple', 4: 'pineapple', 5: 'HERE', 6: 'IS', 7: 'PLAYGROUND!'}
m[100]
# KeyError
m.get(1) # 'have'
m.get(100) # None
m.get(100, 'pen') # 'pen'

for i in m:
	x = m[i]
for i, x in m.items():
	print('#%d' % i)
	print(x)

Function

def my_func(tokens, sep = ','):
	text = sep.join(tokens)
	return text
my_func(tokens) # "HERE,IS,PLAYGROUND!"
my_func(tokens, sep = '!') # "HERE!IS!PLAYGROUND!"

Read and Write

f = open('toRead', 'r')
new_m = {}
for line in f.readlines():
	sentence, order = line[:-1].split('.')
	new_m[sentence] = int(order)

w_f = open('toWrite', 'w')
for sentence in sorted(new_m, key = new_m.__getitem__, reverse = True):
	w_f.write(sentence + '\n')

Regular Expressions

A sequence of characters that define a search pattern

• \b: word boundaries
• \d: digits
• \n: newline
• \r: carriage return
• \s: white space characters
• \t: tab
• \w: alphanumeric characters
• ^: beginning of string
• $: end of string (breaks at newlines!)
• .: any character
• [bdkp]: characters b, d, k and p
• [a-f]: characters a to f
• abc|def: string abc or string def
• *: zero or more times
• +: one or more times
• ?: zero or one time
• {p,q}: at least p times and at most q times
• {p,}: at least p times
• {p}: exactly p times

import re
re.sub(r'foo', 'bar', 'foolish') # 'barlish'