python学习7——函数

1、函数。

def profit(volume, price,cost):
    print("We sell %d ice cream a day." % volume)
    print("You can buy an ice cream at the price of %d dollars" % price)
    print("Make an ice cream will cost us %d dollars." % cost)
    print("Then our daily profit can be %d dollars." %((price-cost)*volume))
print("We can just give the function numbers directly:" )
profit(500,20,10)
print("Or we can use variables from our script:")
volume = 200
price  =10
cost  = 3
profit(volume,price,cost)

输出结果：

 2、函数和文件。

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:
")
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)

输出结果：

为了知道+=的作用，我将代码修改为：

from sys import argv
script, input_file = argv
def print_all(f):
　　print(f.read())
def rewind(f):
　　f.seek(2)
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:
")
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)

输出结果：

可以看到，第二行的内容没有被打印出来。

结论：

a+=b 即为 a=a+b

3、return

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(70,4)
weight=multiply(90,2)
iq = divide(150,2)
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?")

输出结果：