Python seek() 方法

Python seek() 方法

Python seek() 方法用于改变文件句柄的当前位置。文件句柄类似于一个光标，用于定义要在文件中读取或写入的数据的位置。

语法:

fi.seek(offset, from_where), where fi is the file pointer

参数：

Offset： 用于定义向前移动的位置数。

from_where： 用于定义参考点。

注意：Python 中的 seek() 方法不返回任何值。

from_where 参数用于选择参考点。它可以接受三个值：

• 0： 0 值用于将 whence 参数设置为文件开头。
• 1： 1 值用于将 whence 参数设置为文件的当前位置。
• 2： 2 值用于将 whence 参数设置为文件的末尾。

from_where 参数默认设置为 0。因此，在文本模式下，除非偏移量等于 0，否则无法将参考点设置为当前位置或末尾位置。

示例1： （用户需要读取包含以下文本的文本文件：

“This is the sentence I am Writing to show the example of the seek() method working in Python.”

fi = open("text.txt", "r")
# the second parameter of the seek method is by default 0
fi.seek(30)
# now, we will print the current position
print(fi.tell())

print(fi.readline())
fi.close()

输出:

30
ing to show the example of the seek() method working in Python.

示例文本文件 –

# let's assuming the text file has following 5 lines
# line 1: This is the sentence I am Writing to show the example of the seek() 
# method working in Python.
# line 2: The line no. 2 for showing the second method of writing the seek() 
# method is python
# Line 3: the line no. 3 for showing the second method 
# Line 4: the line no. 4 for showing the second method 
# Line 5: the line no. 5 for showing the second method 

示例2：（方法2）

fi = open ("text.txt", "r+")
print ("Name of the file: ", fi.name)

line_1 = fi.readline()
print ("Read Line: %s" % (line_1))

# Again, set the pointer to the beginning
fi.seek (0, 1)
line_2 = fi.readline()
print ("Read Line: %s" % (line_2))

# Close opend file
fi.close()

输出：

Name of the file:  text.txt
Read Line: This is the sentence I am Writing to show the example of the seek() method working in Python.

Read Line: The line no. 2 for showing the second method of writing the seek() method is python

seek() 方法在打开文件为二进制模式时也可以使用负偏移量。

示例3: (负偏移量)

fi = open ("text.txt", "rb")

# the user is setting the reference point to thirtieth position to the left from 
# end
fi.seek (-70, 2)

# now print the current position
print (fi.tell())

# now the user will Convert the binary to string 
print (fi.readline().decode('utf-8'))

fi.close()

输出:

25
 Writing to show the example of the seek() method working in Python.