笨办法学python习题21-30

习题21：函数可以返回某些东西
代码展示

def add(a,b):
    print(f"ADDING {a} + {b}")
    return a + b

def subtract(a,b):
    print(f"SUNTRACTING {a} - {b}")
    return a - b

def multiply(a,b):
    print(f"MULTIPLYING {a} * {b}")
    return a * b

def divide(a,b):
    print(f"DIVIDING {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(f"age:{age},weight:{weight},heihht:{height},iq:{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 becomes:",what,"Can you do it by hand?")

运行结果

习题23：字符串、字节串和字符编码
代码展示

import sys
script,encoding,error = sys.argv

def main(language_file,encoding,errors):
    line = language_file.readline()
    if line:
        print_line(line,encoding,eooros)
        return main(language_file,encoding,errors)

def print_line(line,encoding,errors):
    next_lang = line.strip()
    raw_bytes = next_lang.encode(encoding,errors = errors)
    cooked_string = raw_bytes.decode(encoding,errors = errors)

    print(raw_bytes,"<===>",cooked_string)

languages = open("languages.txt",encoding = "utf-8")

main(languages,encoding,error)

运行截图：


·<===>符号左侧的utf-8每一个字节的数字（十六进制），右侧是输出的字符
·当运行到文件的结尾时，readline函数会返回一个空字符串，if会检查这个空字符串，只要readline函数返回了内容这里就为真
·在main函数的最后调用了main函数，形成循环重复main函数功能，直到if语句结束循环
·print_line函数实质是对language.txt文件中的每一行进行编码
·python中strip的函数详解
·next_lang变量是一个字符串，要获取原始字节串，必须调用.encode()来编码字符串，此时需要把编码的方式和处理错误的方式传入传入encode()函数

习题24：
代码展示

print("Let's practice everything.")
print('You \'d need to know \'bout escapes with \\ that do:')
print('\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 instition
and requires an explanation
\n\t\twhere there is none. 
"""

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

five = 10-2+3-6
print(f"This should be five:{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)
#remember that this is another way to format a string
print("With a starting point of:{}".format(start_point))
#it's just like with an f"" string
print(f"We'd have {beans} beans,{jars} jars,and {crates} crates.")

start_point = start_point / 10

print("We can also do that this way:")
formula = secret_formula(start_point)
#this is a easy way to apply a list to a format string
print("We'd have {} beans,{} jars,and {} crates.".format(*formula))

运行结果

习题25：更多更多的练习
代码展示

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):
    """Take 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)

运行截图

习题29：if语句
代码展示

people = 20
cats = 30
dogs = 15

if people < cats:
    print("Too many cats!The world is doomed!")

if people > cats:
    print("Not many cats!The world is saved!")

if people < dogs:
    print("The world is drooled on!")

if people > dogs:
    print("The world is dry!")

dogs += 5

if people >= dogs:
    print("People are greater than or equal to dogs.")

if people <= dogs:
    print("People are greater than or equal to dogs.")

if people == dogs:
    print("People are dogs.")

运行截图

习题30：else和if
代码展示

people = 30
cars =40
trucks = 15

if cars > people:
    print("We should take the cars.")
elif cars < people:
    print("We should not take the cars.")
else:
    print("We can't decide")
    
if trucks > cars:
    print("That's too many trucks.")
elif trucks < cars:
    print("Maybe we should take the trucks.")
else:
    print("We still can't decide.")

if people > trucks:
    print("Alright,let's just take the trucks.")
else:
    print("Fine,let's stay home then.")

运行截图