Using python to process txts

Answer 1

Dealing with txts in Python mainly involved the following aspects:

* * 1. Open and Close a file **
1. * * Open the file **
- Open the file with the `open ()` function, which accepts two parameters: the file name and the mode to open the file. The common patterns were:
- "r": Open the file in read mode. You can read the file information. If the file does not exist, an error occurs. For example,`file = open ('example.txt','r')`.
- "w": Open the file in write mode, you can write information to the file. If the file exists, clear the file and write new content; if the file does not exist, create it. For example,`file = open ('new_file. txt','w')`.
- "A": Open the file in the appending mode (that is, once the file is opened, the file pointer will automatically move to the end of the file). If the file does not exist, create it. For example,`file = open ('existing-file.txt','a')`.
- "r +": Open the file in read-write mode, allowing you to read and write the file.
- "w +": Erases the contents of the file and then opens the file in read-write mode.
- "A +": Open the file in read-write mode and move the file pointer to the end of the file.
- In addition, you can also use the `with` statement to open the file. The advantage of this statement is that the file will automatically close after the code block is executed. For example,`with open ('data.txt','r') as f: `.
2. * * Close the file **
- If you use the `open ()` function to open the file directly (instead of the `with` statement), you need to use the `close ()` method to close the file after using it. For example,`file. close ()`. This was because if the file was not closed, there was a risk of losing data or damaging the file, and it would take up the number of open file handles in the system.

* * 2. Read the contents of the file **
1. * *`read ()` method **
- It is used to read the entire contents of a file as a string. It accepts the option `size`, which mentions the number of characters to read from the file. If `size` is not set, the entire file will be read. For example:
```python
file = open('example.txt', 'r')
contents = file.read()
print(contents)
file.close()
```
2. * *`readline ()` method **
- It is used to read the file line by line. By default, it reads the first line in the file. You can use a loop to read each line of the file, for example:
```python
file = open('example.txt', 'r')
line = file.readline()
while line:
print(line)
line = file.readline()
file.close()
```
3. * *`readlines ()` method **
- It is used to read all the lines of the file at once and return a list of strings, where each string is a row of data. For example:
```python
file = open('example.txt', 'r')
lines = file.readlines()
for line in lines:
print(line)
file.close()
```

* * 3. Write the contents of the file **
1. * *`write ()` method **
- If you open the file in write ("w ") or add (" a ") mode, you can use the `write ()` method to write the data to the file. For example:
- Open the file in write mode (if the file does not exist, create it, if it does exist, erase it):
```python
file = open('output.txt', 'w')
file.write('Hello, World! ')
file.close()
```
- Open the file in Append mode (Create if the file doesn't exist):
```python
file = open('output.txt', 'a')
file.write('\nThis is a new line. ')
file.close()
```
2. * *`writelines ()` method **
- You can write a line list to a file. For example:
```python
lines = ['line1\n', 'line2\n']
file = open('output.txt', 'w')
file.writelines(lines)
file.close()
```

* * 4. Other methods and attributes in file operation **
1. * * Operation of the file pointer **
- `seek (offset [, where])`: Move the file pointer to the `offset` position relative to `where`.` where `= 0 indicates the beginning of the file (default); 1 indicates the current position; 2 indicates the end of the file.
- `tell ()`: Obtain the file pointer location.
2. * * Other operations **
- `fileno ()`: Obtain the file description, which is a number.
- `flush ()`: Flushes the output buffer.
- `isatty ()`: If the file is an interaction terminal, return `True`; otherwise, return `False`.
- `intercept ([size])`: intercept the file to make it `size`.
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