如何判断 python 变量是否已定义

if 语句

fooVar = 0

# 类似与下面的这种：
if fooVar:
    # pass
else:
    # fooVar = something else...

---

fooVar=0
vardict=dir()
if 'fooVar' in vardict:
print("TRUE")
else:
print("FALSE")

---

try:
  fooVar
except NameError:
  print "well, it WASN'T defined after all!"
else:
  print "sure, it was defined."

我只是搬运工，Determine if variable is defined in Python