"在if语句中调用方法时引发的TypeError:'str'对象不可调用'(Python)

Question

当我在if-block中调用一个方法时,我得到一个TypeError,但是当在if块之外调用它时,该方法会运行find:

randenzyme()从一个叫做酶的词典中随机选择一个键:

def randenzyme(self):
    an_enzyme = choice(self.enzymes.keys())

它运行正常:

x = TCA()
x.randenzyme()

但是"TypeError:'str'对象不可调用"引发:

x = TCA()
user_input = raw_input('> ')
if user_input == "1":
    x.randenzyme()

在if块中调用方法时发生了什么？

更新:这是完整的代码

from random import *
import sys
class TCA(object):
    def __init__(self):
        self.enzymes = {}
        self.enzymes['citrate synthase'] = ('oxaloacetate', 'citrate')
        self.enzymes['aconitase'] = ('citrate', 'isocitrate')
        self.enzymes['isocitrate dehydrogenase'] = ('isocitrate', 'alpha-ketoglutarate')
        self.enzymes['alpha-ketoglutarate dehydrogenase'] = ('alpha-ketoglutarate', 'succinyl-CoA')
        self.enzymes['succinyl-CoA synthetase'] = ('succinyl-CoA', 'succinate')
        self.enzymes['succinate dehydrogenase'] = ('succinate', 'fumarate')
        self.enzymes['fumarase'] = ('fumarate', 'malate')
        self.enzymes['malate dehydrogenase'] = ('malate', 'oxaloacetate')

    def randenzyme(self):
        an_enzyme = choice(self.enzymes.keys())
        print "Reaction (enzyme): %s" % an_enzyme
        return an_enzyme

x = TCA()
print 'Enter "1" for a random enzyme or "2" to exit'
choice = raw_input("> ")
if choice == '1':
    x.randenzyme()
elif choice == '2':
    sys.exit()

我得到的错误是:

Traceback (most recent call last):
File "/Users/sloria1/TCASO.py", line 24, in <module>
x.randenzyme()
File "/Users/sloria1/TCASO.py", line 16, in randenzyme
an_enzyme = choice(self.enzymes.keys())
TypeError: 'str' object is not callable

Answer 1

没有回溯是不可能确定的,但你可能做了像踩踏等傻事choice.