write()方法把字符串str写入文件。没有返回值。由于缓冲，字符串可能不实际显示文件，直到flush()或close()方法被调用。
语法
以下是write()方法的语法：
fileobject.write( str )
参数
str — 这是要被写入的文件中的字符串。
返回值
此方法不返回任何值。
例子
下面的例子显示write()方法的使用。
#!/usr/bin/python
# open a file in write mode
fo = open(“foo.txt”, “rw+”)
print “name of the file: “, fo.name
# assuming file has following 5 lines
# this is 1st line
# this is 2nd line
# this is 3rd line
# this is 4th line
# this is 5th line
str = “this is 6th line”
# write a line at the end of the file.
fo.seek(0, 2)
line = fo.write( str )
# now read complete file from beginning.
fo.seek(0,0)
for index in range(6):
line = fo.next()
print “line no %d – %s” % (index, line)
# close opend file
fo.close()
当我们运行上面的程序，它会产生以下结果：
name of the file: foo.txt
line no 0 – this is 1st line
line no 1 – this is 2nd line
line no 2 – this is 3rd line
line no 3 – this is 4th line
line no 4 – this is 5th line
line no 5 – this is 6th line