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# Learning python 5e page 392 - 415

# CHAPTER 13 while and for Loops

# while test: statements

# if test: break # Exit loop now, skip to else if present

# if test: continue # Go to top of loop now, to test1

# else:

# statements # Run if we didn't hit a 'break'

# for loop

# for target in object: # Assign object items to target

# # statements # Repeated loop body: use target

# # else: # Optional else part

# # statements # If we didn't hit a 'break'

#

# for target in object: # Assign object items to target

# statements

# if test: break # Exit loop now, skip else

# if test: continue # Go to top of loop now

# else:

# statements # If we didn't hit a 'break'

for x in ["spam", "eggs", "ham"]:

print(x, end=' ')

prod = 1

for item in [1, 2, 3, 4]: prod *= item

print(prod)

S = "lumberjack"

for x in S: print(x, end=' ') # Iterate over a string

T = ("and", "I'm", "okay")

for x in T: print(x, end=' ') # Iterate over a tuple

# tuple assignment

T = [(1, 2), (3, 4), (5, 6)]

for (a, b) in T:print(a, b)

# dic assignment

D = {'a': 1, 'b': 2, 'c': 3}

for key in D:

print(key, '=>', D[key]) # Use dict keys iterator and index

for key in D.values():

print(key)

print(list(D.items()))

for (key, value) in D.items():

print(key, '=>', value) # Iterate over both keys and values

for both in T:

a, b = both # Manual assignment equivalent

print(a, b)

for ((a, b), c) in [((1, 2), 3), ((4, 5), 6)]: print(a, b, c) # Nested sequences work

for ((a, b), c) in [([1, 2], 3), ['XY', 6]]: print(a, b, c)

for (a, b, c) in [(1, 2, 3), (4, 5, 6)]: # Used in for loop

print(a, b, c)

for (a, *b, c) in [(1, 2, 3, 4), (5, 6, 7, 8)]:print(a, b, c)

# Nested for loops find same items

items = ["aaa", 111, (4, 5), 2.01]

tests = [(4, 5), 3.14]

for key in tests: # For all keys

for item in items: # For all items

if item == key: # Check for match

print(key, "was found")

break

else:

print(key,"not found!")

for key in tests: # For all keys

if key in items: # Let Python check for a match

print(key, "was found")

else:

print(key, "not found!")

seq1 = "spam"

seq2 = "scam"

res = [] # Start empty

for x in seq1: # Scan first sequence

if x in seq2: # Common item?

res.append(x) # Add to result end

print(x)

[x for x in seq1 if x in seq2] # Let Python collect results

with open("test.txt","w") as file:

file.write("hhhello, ming")

file.write("I_like your cap")

file.write("........")

file.close()

file = open('test.txt')

while True:

line = file.readline() # Read line by line

if not line: break

print(line.rstrip()) # Line already has a \n

# to reverse a file’s lines

for line in reversed([open('test.txt').readlines()]): print(list(line))

# Python code to demonstrate working of

# reversed()

# For string

seqString = 'geeks'

print(list(reversed(seqString)))

# For tuple

seqTuple = ('g', 'e', 'e', 'k', 's')

print(list(reversed(seqTuple)))

# For range

seqRange = range(1, 5)

print(list(reversed(seqRange)))

# For list

seqList = [1, 2, 4, 3, 5]

print(list(reversed(seqList)))

# ord()

# Given a string of length one, return an integer representing the Unicode code

# point of the character when the argument is a unicode object,

# or the value of the byte when the argument is an 8-bit string.

value = ord("A")

value2 = ord("$")

print(value, value2)

# range(a,b,c) a to b-1 by c

print(list(range(5)), list(range(2, 5)), list(range(0, 10, 2)))

for i in range(3):print(i, 'Pythons')

#Sequence Scans: while and range Versus for

i = 0

X= "spam"

while i < len(X): # while loop iteration

print(X[i], end=' ')

i += 1

for i in range(len(X)): print(X[i], end=' ') # Manual range/len iteration

for item in X: print(item, end=' ') # Use simple iteration if you can

S = 'spam'

for i in range(len(S)): # For repeat counts 0..3

S = S[1:] + S[:1] # Move front item to end

print(S, end=' ')

S = 'abcdefghijk'

for c in S[::2]: print(c, end=' ')

L = [1, 2, 3, 4, 5]

for i in range(len(L)):

L[i] += 1

print(L)

#Parallel Traversals: zip and map

# built-in zip function allows us to use for loops to visit multiple sequences

# in parallel—not overlapping in time, but during the same loop.

L1 = [1,2,3,4]

L2 = [5,6,7,8]

print(zip(L1, L2))

print(list(zip(L1, L2)))

for (x, y) in zip(L1, L2):print(x, y, '--', x+y)

T1, T2, T3 = (1,2,3), (4,5,6), (7,8,9)

print(list(zip(T1, T2, T3)))

S1 = 'abc'

S2 = 'xyz123'

print(list(zip(S1, S2))) # only first 3 items are linked

print(list(map(ord, 'spam')))

res = []

for c in 'spam': res.append(ord(c))

print(res)

keys = ['spam', 'eggs', 'toast']

vals = [1, 3, 5]

print(list(zip(keys, vals)))

D2 = {}

for (k, v) in zip(keys, vals): D2[k] = v # creat a dic

print(D2)

{k: v for (k, v) in zip(keys, vals)} # another way

# Generating Both Offsets and Items: enumerate

S = 'spam'

offset = 0

for item in S:

print(item, 'appears at offset', offset)

offset += 1

# enumerate!!!

S = 'spam'

for (offset, item) in enumerate(S):

print(item, 'appears at offset', offset)

E = enumerate(S)

print(next(E))

print(next(E))

print(next(E))

[c * i for (i, c) in enumerate(S)]

for (i, l) in enumerate(open('test.txt')):print('%s) %s' % (i, l.rstrip()))