python文件操作

python文件操作

1、从文件中读取数据

1.1、读取整个文件

新建一个txt文本文件:

is_digits.txt

3.1415926535
8979323846
2643383279

新建一个.py文件

1 # -*-coding:utf-8 -*-
2 
3 with open("pi_digits.txt") as file_object:
4     contents = file_object.read()
5     print(contents)

执行结果:

3.1415926535
8979323846
2643383279

 

1.2、文件路径:

通过文件所在路径,进行文本读取操作

1 #文件路径
2 
3 file_path = 'C:\pycharm\python3\pi_digits.txt'
4 
5 with open(file_path) as file_object:
6     contents = file_object.read()
7     print(contents.rstrip()) #rstrip()是删除文本末尾的空白

执行结果:

3.1415926535
8979323846
2643383279

1.3、逐行读取

对文本的每一行进行读取操作:

1 #逐行读取
2 
3 with open('pi_digits.txt') as file_object:
4     for line in file_object:
5         print(line)

执行结果:


3.1415926535


8979323846


2643383279

 

如何消除多余的空白呢,使用rstrip()函数

with open('pi_digits.txt') as file_object:
    for line in file_object:
        # print(line)
        print(line.rstrip())

执行结果:

3.1415926535
8979323846
2643383279

 

1.3、创建一个包含文件各行内容的列表

知识点:

  1. readlines()
  2. for ... in ... 循环
  3. str.rstrip()函数

 

实例:

1 #创建一个包含文件各行的内容
2 
3 filename = "pi_digits.txt"
4 
5 with open(filename) as file_objects:
6     lines = file_objects.readlines()
7 
8     for line in lines:
9         print(line。rstrip())

执行结果:

3.1415926535
8979323846
2643383279

 

1.4、使用文件的内容

 

#使用文件的内容

filename = "pi_digits.txt"

with open(filename) as file_objects:
lines = file_objects.readlines()

pi_string = '' #定义一个空字符串
for line in lines:
pi_string += line.rstrip() #将每一行的数字进行加法(也就是放到一行中),并且删除多余空格

print(pi_string)
print(len(pi_string)) #打印字符串长度

执行结果:

3.141592653589793238462643383279
32

 

2、写入文件

保存数据的最简单方式就是把它写到文件中。

2.1、写入空文件

方法:

  1. 'w' :表示写入模式
  2. ‘r’:表示读取模式
  3. ‘a’:表示附加模式
  4. write():文件对象写入方法

实例:

1 #写入空文件
2 filename = "new_file.txt"  #定义一个文件名称
3 
4 with open(filename,'w') as file_object: # 'w'表示读取模式
5     file_object.write('I love python.')

执行结果:

python文件操作

 

2.2、写入多行

 注意审题,是写入多行,而不是一行哦。

代码:

1 #写入多行
2 
3 filename = 'new_file2.txt'
4 with open(filename,'w') as file_object:
5     file_object.write('Hello,world.')
6     file_object.write("As the old saying goes, where there's a will, there's a way")

输出结果:

Hello,world.As the old saying goes, where there's a will, there's a way

怎么样才能进行换行操作实现多行呢,   使用 “\n”

代码:

1 filename = 'new_file2.txt'
2 with open(filename,'w') as file_object:
3     file_object.write('Hello,world.\n')
4     file_object.write("As the old saying goes, where there's a will, there's a way\n")

输出:

Hello,world.
As the old saying goes, where there's a will, there's a way

 

2.3、附加到文件

如果想在原有的文件基础上继续增加内容,而不是每次都新建一个新文件,怎么操作呢,这里使用附件操作。

知识点:

  1.  ‘a’:附件模式
  2. ‘r+’:读取和写入模式

实例:

1 #附件模式
2 filename = 'new_file2.txt'
3 with open(filename,'a') as file_object:
4     file_object.write('Thinking is impossible.\n')
5     file_object.write('That is ok\n')

执行结果:

1 Hello,world.
2 As the old saying goes, where there's a will, there's a way
3 Thinking is impossible.
4 That is ok
5 Thinking is impossible.
6 That is ok

方法2:

1 #方法2:r+模式
2 filename = 'new_file2.txt'
3 with open(filename,'r+') as file_object:
4     file_object.write(' process finished with exit code 0.\n')

结果:

 process finished with exit code 0.
 0.
e there's a will, there's a way
Thinking is impossible.
That is ok
Thinking is impossible.
That is ok

 

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