# one bar放到前面
def bar():
print("from bar")
def foo():
print("from foo")
bar()
foo()
# one bar放到下面, 先加载foo和bar到内存中,再调用foo函数
def foo():
print("from foo")
bar()
def bar():
print("from bar")
foo()
"""
# NameError: name 'bar' is not defined
def foo():
print("from foo")
bar()
foo()# 指定到这里的时候bar还没有加载到内存.
def bar():
print("from bar")
"""