为什么我在 globals() 中找不到我的变量？

Question

I created a function to create a variable for random DNA. But when I want to look if rdna is in globals() I get False as result

from random import choice
def randomseq():
  global rdna
  rdna=""
  largo = int(input("Sequence Length: "))
  for count in range(largo):
    rdna+=choice("CGTA")
  return rdna

rdna in globals()
False

Why can't I get True ?

Answer 1

rdna in globals() will search for the value stored in the variable rdna in globals() . If you literally want to search for "rdna" you should make it a string literal:

"rdna" in globals()

Answer 2

Take this example:

x = 1
my_var = 'x'
print(my_var in globals())

This prints True , but not because my_var is a global variable, but because x is. globals() returns a dictionary with all global variables and their values, my_var in globals() in this case is the same as asking 'x' in globals() .

You want this:

'rdna' in globals()