Python 入门教程 5 ---- Conditionals & Control Flow

 第一节

     1 介绍Python利用有6种比较的方式 == , != , > , >= , < , <=

     2 比较后的结果是True或者是False

     3 练习

        1 把bool_one的值设置为 17 < 118%100

        2 把bool_two的值设置为 100 == 33*3 + 1

        3 把bool_two的值设置为 19 <= 2**4

        4 把bool_four的值设置为 -22 >= -18

        5 把bool_five的值设置为 99 != 98+1

#Assign True or False as appropriate on the lines below!bool_one = 17 < 118%100bool_two = 100 == 33*3+1bool_three = 19 <= 2**4bool_four = -22 >= -18bool_five = 99 != 98+1

 第二节

    1 介绍了比较的两边不只是数值，也可以是两个表达式

    2 练习

       1 把bool_one的值设置为 20 + -10*2 > 10%3%2

       2 把bool_two的值设置为 (10+17)**2 == 3**6

       3 把bool_two的值设置为 1**2**3 <= -(-(-1))

       4 把bool_four的值设置为 40/20*4 >= -4**2

       5 把bool_five的值设置为 100**0.5 != 6+4

# Assign True or False as appropriate on the lines below!bool_one = 20+-10*2 > 10%3%2bool_two = (10+17)**2 == 3**6bool_three = 1**2**3 <= -(-(-1))bool_four = 40/20*4 >= -4**2bool_five = 100**0.5 != 6+4

 第三节

    1 介绍了Python里面还有一种数据类型是booleans，值为True或者是False

    2 练习：根据题目的意思来设置右边的表达式

# Create comparative statements as appropriate on the lines below!# Make me true!bool_one = 1 <= 2# Make me false!bool_two = 1 > 2# Make me true!bool_three = 1 != 2# Make me false!bool_four = 2 > 2# Make me true!bool_five = 4 < 5

 第四节

    1 介绍了第一种连接符and的使用，只有and的两边都是True那么结果才能为True

    2 练习

       1 设置变量bool_one的值为False and False

       2 设置变量bool_two的值为-(-(-(-2))) == -2 and 4 >= 16**0.5

       3 设置变量bool_three的值为19%4 != 300/10/10 and False

       4 设置变量bool_four的值为-(1**2) < 2**0 and 10%10 <= 20-10*2

       5 设置变量bool_five的值为True and True

bool_one = False and Falsebool_two = -(-(-(-2))) == -2 and 4 >= 16**0.5bool_three = 19%4 != 300/10/10 and Falsebool_four = -(1**2) < 2**0 and 10%10 <= 20-10*2bool_five = True and True

 第五节

    1 介绍了第二种连接符or的使用，只要or的两边有一个True那么结果才能为True

    2 练习

       1 设置变量bool_one的值为2**3 == 108%100 or 'Cleese' == 'King Arthur'

       2 设置变量bool_two的值为True or False

       3 设置变量bool_three的值为100**0.5 >= 50 or False

       4 设置变量bool_four的值为True or True

       5 设置变量bool_five的值为1**100 == 100**1 or 3*2*1 != 3+2+1

bool_one = 2**3 == 108%100 or 'Cleese' == 'King Arthur'bool_two = True or Falsebool_three = 100**0.5 >= 50 or Falsebool_four = True or Truebool_five = 1**100 == 100**1 or 3*2*1 != 3+2+1

 第六节

    1 介绍第三种连接符not , 如果是not True那么结果为False，not False结果为True

    2 练习

       1 设置变量bool_one的值为not True

       2 设置变量bool_two的值为not 3**4 < 4**3

       3 设置变量bool_three的值为not 10%3 <= 10%2

       4 设置变量bool_four的值为not 3**2+4**2 != 5**2

       5 设置变量bool_five的值为not not False

bool_one = not Truebool_two = not 3**4 < 4**3bool_three = not 10%3 <= 10%2bool_four = not 3**2+4**2 != 5**2bool_five = not not False

 第七节

    1 介绍了由于表达式很多所以我们经常使用()来把一些表达式括起来，这样比较具有可读性

    2 练习

       1 设置变量bool_one的值为False or (not True) and True

       2 设置变量bool_two的值为False and (not True) or True 

       3 设置变量bool_three的值为True and not (False or False)

       4 设置变量bool_four的值为not (not True) or False and (not True)

       5 设置变量bool_five的值为False or not (True and True)

bool_one = False or (not True) and Truebool_two = False and (not True) or True bool_three = True and not (False or False)bool_four = not (not True) or False and (not True)bool_five = False or not (True and True)

 第八节

    1 练习：请至少使用and，or，not来完成以下的练习

# Use boolean expressions as appropriate on the lines below!# Make me false!bool_one = not ((1 and 2) or 3)# Make me true!bool_two = not (not((1 and 2) or 3))# Make me false!bool_three = not ((1 and 2) or 3)# Make me true!bool_four = not (not((1 and 2) or 3))# Make me true!bool_five = not (not((1 and 2) or 3)

 第九节

    1 介绍了条件语句if

    2 if的格式如下, 比如

if 8 < 9:    print "Eight is less than nine!"

    3 另外还有这elif 以及else，格式如下

if 8 < 9:    print "I get printed!"elif 8 > 9:    print "I don't get printed."else:    print "I also don't get printed!"

     4 练习：设置变量response的值为'Y'

response = 'Y'answer = "Left"if answer == "Left":    print "This is the Verbal Abuse Room, you heap of parrot droppings!"    # Will the above print statement print to the console?# Set response to 'Y' if you think so, and 'N' if you think not.

 第十节

    1 介绍了if的格式

if EXPRESSION:    # block line one    # block line two    # et cetera

    2 练习：在两个函数里面加入两个加入条件语句，能够成功输出

def using_control_once():    if 1 > 0:        return "Success #1"def using_control_again():    if 1 > 0:        return "Success #2"print using_control_once()print using_control_again()

 第十一节

     1 介绍了else这个条件语句

     2 练习：完成函数里面else条件语句

answer = "'Tis but a scratch!"def black_knight():    if answer == "'Tis but a scratch!":        return True    else:                     return False       # Make sure this returns Falsedef french_soldier():    if answer == "Go away, or I shall taunt you a second time!":        return True    else:                     return False       # Make sure this returns False

 第十二节

     1 介绍了另外一种条件语句elif的使用

     2 练习：在函数里面第二行补上answer > 5， 第四行补上answer < 5 , 从而完成这个函数

def greater_less_equal_5(answer):    if answer > 5:        return 1    elif answer < 5:                 return -1    else:        return 0        print greater_less_equal_5(4)print greater_less_equal_5(5)print greater_less_equal_5(6)

 第十三节

    1 练习：利用之前学的比较以及连接符以及条件语句补全函数。所有的都要出现至少一次

def the_flying_circus():    # Start coding here!    if 1 < 2 and not False:        return True    elif 1 == 1 or 1 != 2 or 1 < 2 or 1 <= 2 or 1 > 2 or 1 >= 2:        return True    else:        return False