Learn Python The Hard Way-Ecercise21~25

Exercise21：函数可以返回东西

def add(a, b): #定义四则运算的函数
	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 "MULTIPLY %d * %d" % (a, b)
	return a * b

def divide(a, b):
	print "DIVIDE %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)


# A puzzle for the extra credit, type it in anyway.
print "Here is a puzzle."

what = add(age, subtract(height, multiply(weight, divide(iq, 2))))

print "That become: ", what, "Can you do it by hand?"

输出结果：

$ python ex21.py
Let's do some math with just functions!
ADDING 30 + 5
SUBTRACTING 78 - 4
MULTIPLYING 90 * 2
DIVIDING 100 / 2
Age: 35, Height: 74, Weight: 180, IQ: 50
Here is a puzzle.
DIVIDING 50 / 2
MULTIPLYING 180 * 25
SUBTRACTING 74 - 4500
ADDING 35 + -4426
That becomes: -4391 Can you do it by hand?

Exercise22：你到现在学到了哪些东西？

Exercise23：读代码

Exercise24：更多练习

print "Let's practice everything."
print 'You\'d need to know \' bout escapes with \\ that do \n newlines and \t tabs.'

poem = """
\tThe lovely world
with logic so firmly planted
cannot discern \n the needs of love
nor comprehend passion from intuition
and requires an explanation
\n\t\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)

输出结果：

$ python ex24.py
Let's practice everything.
You'd need to know 'bout escapes with \ that do
newlines and
tabs.
--------------
The lovely world
with logic so firmly planted
cannot discern
the needs of love
nor comprehend passion from intuition
and requires an explanation
where there is none.
--------------
This should be five: 5
With a starting point of: 10000
We'd have 5000000 beans, 5000 jars, and 50 crates.
We can also do that this way:
We'd have 500000 beans, 500 jars, and 5 crates.

Exercise25：更多更多的练习

def break_words(stuff):
	"""This function will break up words for us."""
	words = stuff.split(' ')
	return words

def sort_words(words):
	"""Sorts the words."""
	return sorted(words)

def print_first_word(words):
	"""Prints the first word after popping it off."""
	word = words.pop(0)
	print word

def print_last_word(words):
	"""Prints the last word after popping it off."""
	word = words.pop(-1)
	print word

def sort_sentence(sentence):
	"""Takes in a full sentence and returns the sorted words."""
	words = break_words(sentence)
	return sort_words(words)

def print_first_and_last(sentence):
	"""Prints the first and last words of the sentence."""
	words = break_words(sentence)
	print_first_word(words)
	print_last_word(words)

def print_first_and_last_sorted(sentence):
	"""Sorts the words then prints the first and last one."""
	words = sort_sentence(sentence)
	print_first_word(words)
	print_last_word(words)

输出结果：

$ python
2 Python 2.5.1 (r251:54863, Feb
3 [GCC 4.0.1 (Apple Inc. build 5465)] on darwin
4 Type "help", "copyright", "credits" or "license" for more information.
5 >>> import ex25
6 >>> sentence = "All good things come to those who wait."
7 >>> words = ex25.break_words(sentence)
8 >>> words
9 ['All', 'good', 'things', 'come', 'to', 'those', 'who', 'wait.']
6 2009, 19:02:12)
10 >>> sorted_words = ex25.sort_words(words)
11 >>> sorted_words
12 ['All', 'come', 'good', 'things', 'those', 'to', 'wait.', 'who']
13 >>> ex25.print_first_word(words)
14 All
15 >>> ex25.print_last_word(words)
16 wait.
17 >>> wrods
18 Traceback (most recent call last):
File "<stdin>", line 1, in <module>
19
20 NameError: name 'wrods' is not defined
21 >>> words
22 ['good', 'things', 'come', 'to', 'those', 'who']
23 >>> ex25.print_first_word(sorted_words)
24 All
25 >>> ex25.print_last_word(sorted_words)
26 who
27 >>> sorted_words
28 ['come', 'good', 'things', 'those', 'to', 'wait.']
29 >>> sorted_words = ex25.sort_sentence(sentence)
30 >>> sorted_words
31 ['All', 'come', 'good', 'things', 'those', 'to', 'wait.', 'who']
32 >>> ex25.print_first_and_last(sentence)
33 All
34 wait.
35 >>> ex25.print_first_and_last_sorted(sentence)
36 All
37 who
38 >>> ^D
39 $