Python seek()方法用于更改文件句柄的当前位置。文件句柄就像一个光标，用于定义必须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:
偏移量: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 值用于设置文件开头的 what 参数。
- 1:1 值用于在文件的当前位置设置 whence 参数。
- 2:2 值用于设置文件末尾的 what 参数。
默认情况下，from_where 参数设置为 0。因此，在文本模式下，参考点不能设置为当前位置或结束位置，除非偏移量等于 0。
示例 1: (用户必须读取包含以下文本的文本文件:
“这是我写的句子，展示了在 Python 中使用 seek()方法的例子。”
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
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()方法也可以使用负偏移量，但只能在文件以二进制模式打开时使用。
例 3:(负偏移)
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.
