python 零起点(4)

函数和文件

 1 from sys import argv
 2 
 3 script, input_file = argv
 4 
 5 def print_all(f):
 6     print f.read()
 7 
 8 def rewind(f):
 9     f.seek(0)
10 
11 def print_a_line(line_count, f):
12     print line_count, f.readline()
13 
14 current_file = open(input_file)
15 
16 print "First let's print the whole file:\n"
17 
18 print_all(current_file)
19 
20 print "Now let's rewind, kind of like a tape."
21 
22 rewind(current_file)
23 
24 print "Let's print three lines:"
25 
26 current_line = 1
27 print_a_line(current_line, current_file)
28 
29 current_line = current_line + 1
30 print_a_line(current_line, current_file)
31 
32 current_line = current_line + 1
33 print_a_line(current_line, current_file)
34

：定义了三个函数
print_all() 直接输出文本内容
rewind(f) 转到文件的 0 byte 也就是第一个 byte 的位置
print_a_line() 有行数的输出

current_line = 1 第一行

def add(a, b):
    print "ADDING %d + %d" % (a, b)
    return a + b

add(50+20,2+5)

#函数返回的值是77

PS：函数可返回值

导入函数？