Python IDLE 回溯错误

Question

I am trying to learn Python on my own. I created a Python file to to print Hello, world! My Python file (called test), which I did not save in the IDLE or Python library, is:

def hello():                                             
    print "Hello,world!"

When I ran this file in the Python shell as hello(),the error was:

Traceback (most recent call last):
File "<pyshell#2>", line 1, in <module>
hello
NameError: name 'hello' is not defined

Can you help me troubleshoot the cause of this problem?

Answer 1

I'm guessing your full code is something like this:

hello() # this hasn't been defined yet

def hello():
    println "Hello, world!"

When you call hello() on line 1, the function has not been defined yet because Python executes that script from the start to the end. Move the function call below the function:

def hello():
    println "Hello, world!"

hello() # now Python knows what hello is