with statement is a context management method for opening and closing files. For example, the general opening posture is
file = open("filename", 'wb')
# do something
file.close()
With context management, withAfter the code block is executed, the internal method will be called to directly close the file. There is no need to manually call the close() method, which is the way given in the question. Of course format is a method of formatting strings. The position of {n} is reserved in the string. n will be used as the key of a keyword parameter. After the value is passed in, the passed in will be used. valuereplacement, so the position of {n:02d} in the question will be replaced by the integer string received by n. If only {} is left in the string, and no key value is specified, then the parameter passed in format will be used as a positional parameter, and will be filled in order one by one corresponding to the {} in the string.
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
The
withstatement is a context management method for opening and closing files. For example, the general opening posture isWith context management,
withAfter the code block is executed, the internal method will be called to directly close the file. There is no need to manually call theclose()method, which is the way given in the question.Of course
formatis a method of formatting strings. The position of{n}is reserved in the string.nwill be used as the key of a keyword parameter. After the value is passed in, the passed inwill be used. valuereplacement, so the position of{n:02d}in the question will be replaced by the integer string received byn. If only{}is left in the string, and no key value is specified, then the parameter passed informatwill be used as a positional parameter, and will be filled in order one by one corresponding to the{}in the string.Format string
Equivalent to:
"map" + "00" + ".png"