python 零起点(4)

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:\n"

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)
 

：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？