习题18：
def print_two(*args):
arg1,arg2 = args
print("arg1:%r,arg2:%r" %(arg1,arg2))

def print_two_again(arg1,arg2):
print("arg1:%r,arg2:%r" %(arg1,arg2))

def print_one(arg1):
print("arg1:%r" % arg1)

def print_none():
print("I got nothin")

print_two("zed","shaw")
print_two_again("zed","shaw")
print_one("first!")
print_none()

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习题19：
def cheese_and_crackers(cheese_count,boxes_and_crackers):
print("you have cheese! %r" % cheese_count)
print("you have boxes and crackers! %d" % boxes_and_crackers)
print("man that's enough for a party!")
print("get a blanket.\n")
print("We can just give the function numbers directly:")
cheese_and_crackers (20,30)
print("We can use variables from our script:")
amount_of_cheese = 10
amount_of_crackers = 50

cheese_and_crackers(amount_of_cheese,amount_of_crackers)
print("We can even do math inside too:")
cheese_and_crackers(10+20,5+6)
print("And we can combine the two, variables and math:")
cheese_and_crackers(amount_of_cheese+100,amount_of_crackers+1000)
···

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···
习题20：
from sys import argv
script, input_file = argv
def print_all(f):
print(f.read())
def rewind(f):
f.seek(0)
def print_a_line(line_count, f):
print(line_count, f.readline())
current_file = open(input_file)
print("First let's print the whole file:\n")
print_all(current_file)
print("Now let's rewind, kind of like a tape.")
rewind(current_file)
print("Let's print three lines:")
current_line = 1
print_a_line(current_line, current_file)
current_line = current_line + 1
print_a_line(current_line, current_file)
current_line = current_line + 1
print_a_line(current_line, current_file)

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习题21
def add(a, b):
print("ADDING %d + %d" % (a, b))
return a + b
def subtract(a, b):
print("SUBTRACTING %d - %d" % (a, b))
return a - b
def multiply(a, b):
print("MULTIPLYING %d * %d" % (a, b))
return a * b
def divide(a, b):
print("DIVIDING %d / %d" % (a, b))
return a / b
print("Let's do some math with just functions!")
age = add(30, 5)
height = subtract(78, 4)
weight = multiply(90, 2)
iq = divide(100, 2)
print("Age: %d, Height: %d, Weight: %d, IQ: %d" % (age, height,weight, iq))
print("Here is a puzzle.")
what = add(age, subtract(height, multiply(weight, divide(iq,2))))
print("That becomes: ", what, "Can you do it by hand?")

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习题24：
print("let's practice everything.")
print("you'd need to know 'bout escapes with \ that do \n newlines and \t tabs.")

poem=""" \t The lovely world with logic so firmly planted cannot discern \n
the needs of love nor comprehend passion from intuition and requires an explanation
\n\twhere there is none."""

print("-------------")
print(poem)
print("-------------")

five=10-2+3-6
print("This should be five: %s" %five)

def secret_formula(started):
jelly_beans=started*500
jars=jelly_beans/1000
crates=jars/100
return jelly_beans,jars,crates

start_point=10000
beans, jars, crates=secret_formula(start_point)

print("With a starting point of:%d" % start_point)
print("We'd have %d beans, %d jars, and %d crates." % (beans, jars, crates))

start_point=start_point/10

print("We can also do that this way:")
print("We'd have %d beans, %d jars, and %d crates." % secret_formula(start_point))

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本周一直在加班各种忙的不行，今天周日休息，抓紧时间做了作业题，其实我只是在敲代码，然后去执行，发现错误去改正，真正让我去编代码，估计差得还远折呢。
程序员的工作真的不容易呀！

25、26没有搞出来，可能是我没有理解题目的意思。