尝试写入文件什么也没有

Question

当尝试在 python 中读取文件时，它似乎只打印出一个空格而不是“测试消息”，这是我的代码：

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w+') as file:
        file.write(contents)
        print(file.read())

    
    
readAndWritetofile()

Answer 1

你忘了

file.seek(0)

第 6 行之前

Answer 2

写入后，文件指针位于文件末尾。您可以回到起点或重新开始。

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w+') as file:
        file.write(contents)
        file.seek(0)
        print(file.read())

readAndWritetofile()

或

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w') as file:
        file.write(contents)
        # exit the with closes the file
    with open("file.txt") as file:
        print(file.read())

readAndWritetofile()

Answer 3

您应该添加file.seek(0)。如果您忘记了这一点，file.read() 调用将尝试从文件末尾读取，并返回一个空字符串。

当前，指针位于文件末尾。 file.seek(0)将其移至文件开头。

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w+') as file:
        file.write(contents)
        file.seek(0)
        print(file.read())

readAndWritetofile()