笨办法学Python3 习题20

基于Python3.6

习题20

from sys import argv
#从命令行输入要读取的文件
script, input_file = argv
#定义输入全部文件内容的函数
def print_all(f):
    print(f.read())
#seek()方法用于移动文件读取指针到指定位置,0是文件开头
def rewind(f):
    f.seek(0)
#定义打印某一行的文件函数，readline()自动换行
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)