• 《Python for Beginners》学习笔记(3)


    《Python for Beginners》为LearnStreet上的Python入门课程。本节主要学习内容为条件语句

    Lesson 4  Control Flow and Conditionals

    1. 第一个Python函数

     1 def check_wounds():
     2     #your code here
     3     arms = 0
     4     if arms == 1:
     5         return "tis but a scratch"
     6     elif arms == 0:
     7         return "flesh wound"
     8     else:
     9         return "cross bridge"
    10 
    11 #This is just for you to see what happens when the function is called
    12 print check_wounds()

    输出结果:
    flesh wound

    2. if语句

    1 def always_true():
    2     if 1 == 1:
    3         #insert your code here
    4         return "complete"
    5 
    6 #This is just for you to see what happens when the function is called
    7 print always_true()

    输出结果:
    complete

    3. 再来一个if语句

    1 flag = "unchanged"
    2 def always_false():
    3     global flag
    4     if 1==2:
    5         flag = "changed"
    6 
    7 #This is just for you to see what happens when the function is called
    8 always_false()
    9 print flag

    输出结果:
    unchanged

    4. else语句

     1 def check_condition():
     2     #return this if the condition is True
     3     ifRun = "if code block run" 
     4 
     5     #return this is if the condition is False
     6     elseRun = "else code block run" 
     7     
     8     condition = 0
     9 
    10     if condition == True:
    11         #your code here
    12         return ifRun
    13     else:
    14         #your code here
    15         return elseRun
    16 
    17 #This is just for you to see what happens when the function is called
    18 print check_condition()

    输出结果:
    else code block run

    5. elif语句

     1 def colorful_conditions():
     2 
     3     color = "blue"
     4 
     5     if  color == "red":
     6         return "first block"
     7     elif  color == "white":
     8         return "second block"
     9     elif  color == "blue":
    10         return "third block"
    11     else:
    12         return "fourth block"
    13 
    14 #This is just for you to see what happens when the function is called
    15 print colorful_conditions()

    输出结果:
    third block

    6. if语句练习
    问题:
    When the string phrase is fewer than 30 characters long, return 1. When it is exactly 30 return 2, and when it is greater than 30 return 3.

    代码:

     1 def check_length(phrase):
     2     # your if condition here
     3     if len(phrase) < 30:
     4         return 1
     5     # your elif condition here
     6     elif len(phrase) == 30:
     7         return 2
     8     # your else condition here
     9     else:
    10         return 3
    11 
    12 #This is just for you to see what happens when the function is called
    13 print check_length("hi, i am a phrase")

    输出结果:
    1

    7. if语句练习2

     1 """
     2 This function should check the value of the num variable and
     3 return the string representation of the interval it is in  Use if, elif,
     4 and else statements to check if num falls in the range 1-5, 6-10,
     5 11-15, or 16-20. Then return the correct interval as a string, like 
     6 "1-5", "6-10", "11-15", or "16-20".
     7 """
     8 def check_interval():
     9     #Your code here
    10     num = 5
    11     if num < 6:
    12         return "1-5"
    13     elif num < 11:
    14         return "6-10"
    15     elif num < 16:
    16         return "11-15"
    17     else:
    18         return "16-20"
    19 
    20 #This is just for you to see what happens when the function is called
    21 print check_interval()

    输出结果:
    1-5

    8. and操作符

    1 def should_eat(hungry, awake):
    2     #your if statement here
    3     if hungry and awake:
    4         return "eat"
    5     else:
    6         return "don't eat"
    7 
    8 #This is just for you to see what happens when the function is called
    9 print should_eat(True, True)

    输出结果:
    eat

    9. or操作符

    1 def kitchen_or_bed(hungry, thirsty):
    2     # your if statement here
    3     if hungry or thirsty:
    4         return "go to kitchen"
    5     else:
    6         return "go to bed"
    7 
    8 #This is just for you to see what happens when the function is called
    9 print kitchen_or_bed(True, True)

    输出结果:
    go to kitchen

    10. 复习

     1 def who_are_you(green, large):
     2     # Write if-elif-else statements below
     3     if green and large:
     4         return "hulk"
     5     elif green:
     6         return "alien"
     7     elif large:
     8         return "elephant"
     9     else:
    10         return "Bruce Banner"
    11 
    12 #This is just for you to see what happens when the function is called
    13 print who_are_you(True, True)

    输出结果:
    hulk

    总结:
    1)注意缩进的格式
    2)#开头为注释一行代码
    3)注意函数定义以及条件语句后面的冒号
    4)字符串可以直接作为函数的实参

    (本文完)

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  • 原文地址:https://www.cnblogs.com/geekham/p/2946727.html
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