“笨办法”学Python3--习题20 函数和文件

目录

 

函数与文件

print后不自动换行

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函数与文件

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("let's rewind ,kind of like a tape.")
rewind(current_file)

print("Let's ptint three lines:")

current_line = 1
print_a_line(current_line,current_file)
current_line = 1+current_line
print_a_line(current_line,current_file)
current_line = 1+current_line
print_a_line(current_line,current_file)

Python里的文件就像磁带/DVD一样，有一个用来读取数据的“磁头”，可以通过它来操作文件，每次运行f.seek(0)就回到了文件的起始位置，而f.readline()则会读取文件的一行，然后把“磁头”移动到\n的后面去。

print后不自动换行

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(),end="")#print添加参数end=“”，不会自动换行了

current_file = open(input_file)

print("First let's print the whole file:")
print_all(current_file)

print("let's rewind ,kind of like a tape.")
rewind(current_file)

print("Let's ptint three lines:")

current_line = 1
print_a_line(current_line,current_file)
current_line = 1+current_line
print_a_line(current_line,current_file)
current_line = 1+current_line
print_a_line(current_line,current_file)