python中两个for实例_python for循环有两个实例

我正在学习和刻苦学习python。在消费税41中，我有一些难以理解的代码。

我在下面的代码中有一个问题：

for sentence in snippet, phrase:

result = sentence[:]两个对象内的for循环如何。我无法理解这一点。片段是关键之一。在PHRASES字典中将该键的值写下。在我的选择中，循环必须在一个列表或元组中。但不能两个对象。

我的理解错了吗？

完整的代码信息

import random

from urllib import urlopen

import sys

WORD_URL = "http://learncodethehardway.org/words.txt"

WORDS = []

PHRASES = {

"class %%%(%%%):":

"Make a class named %%% that is -a %%%.",

"class %%%(object):ntdef __init__(self, ***)":

"class %%% has -a __init__ that takes self and *** parameters.",

"class %%%(object):ntdef ***(self, @@@)":

"class %%% has -a fucntion named *** that takes self and @@@ parameters.",

"*** = %%%()":

"Set *** to an instance of class %%%.",

"***.***(@@@)":

"From *** get the *** function, and call it with parameters self, @@@.",

"***.*** = '***'":

"From *** get the *** attribute and set it to '***'."

}

# do they want to drill phrase first

if len(sys.argv) == 2 and sys.argv[1] == "english":

PHRASES_FIRST = True

else:

PHRASE_FIRST = False

# load up the words from the website

for word in urlopen(WORD_URL).readlines():

WORDS.append(word.strip())

def convert(snippet, phrase):

class_names = [w.capitalize() for w in

random.sample(WORDS, snippet.count("%%%"))]

other_names = random.sample(WORDS, snippet.count("***"))

results = []

param_names = []

for i in range (0,snippet.count("@@@")):

param_count = random.randint(1,3)

param_names.append(', '.join(random.sample(WORDS,param_count)))

for sentence in snippet, phrase:

result = sentence[:]

# fake class names

for word in class_names:

result = result.replace("%%%", word,1)

# fake other names

for word in other_names:

result = result.replace("***", word, 1)

# fake parameter list

for word in param_names:

result = result.replace("@@@", word, 1)

results.append(result)

return results

# keep going until they hit CTRL-D

try:

while True:

snippets = PHRASES.keys()

random.shuffle(snippets)

for snippet in snippets:

phrase = PHRASES[snippet]

question, answer = convert(snippet, phrase)

if PHRASES_FIRST:

question, answer = answer, question

print question

raw_input("> ")

print "ANSWER: %snn" % answer

except EOFError:

print "nBye"