#!/usr/bin/env python

-*- coding: utf-8 -*-

def count_words(filename):
"""计算一个文件大致包含多少个单词"""
try:
with open(filename) as file_object:
contents=file_object.read()
except FileNotFoundError:
message="Sorry,the file "+filename+" does not exist."
print(message)
else:
#计算文件大致包含多少个单词
words=contents.split()
num_words=len(words)
print("The file "+filename+" has about "+str(num_words)+" words.")
filenames=['alice.txt','siddhartha.txt','moby_dick.txt','little_women.txt']
for filename in filenames:
count_words(filename)

其中siddhartha.txt不在文件夹内，想请问一下这是什么情况~

函数也需要缩进，按下面这段试下：

#!/usr/bin/env python
-*- coding: utf-8 -*-
def count_words(filename):
"""计算一个文件大致包含多少个单词"""
    try:
            with open(filename) as file_object:
                    contents=file_object.read()
            except FileNotFoundError:
                    message="Sorry,the file "+filename+" does not exist."
            print(message)
    else:
            #计算文件大致包含多少个单词
            words=contents.split()
            num_words=len(words)
            print("The file "+filename+" has about "+str(num_words)+" words.")
            filenames=['alice.txt','siddhartha.txt','moby_dick.txt','little_women.txt']
            for filename in filenames:
                    count_words(filename)

哥们，python要求严格的冒号过行后要留一个tab缩进，另外不知道你下面的else哪来的，给的注释掉了，以后这种error多查google
def count_words(filename):
"""计算一个文件大致包含多少个单词"""
try:
with open(filename) as file_object:
contents=file_object.read()
except FileNotFoundError:
message="Sorry,the file "+filename+" does not exist."
print(message)
#else:
#计算文件大致包含多少个单词
words=contents.split()
num_words=len(words)
print("The file "+filename+" has about "+str(num_words)+" words.")
filenames=['alice.txt','siddhartha.txt','moby_dick.txt','little_women.txt']
for filename in filenames:
count_words(filename)

try后面的语句都没有进行缩进呢

如楼上所说，Python是用缩进控制代码的，你按下面这段试下？

#!/usr/bin/env python
-*- coding: utf-8 -*-
def count_words(filename):
"""计算一个文件大致包含多少个单词"""
try:
    with open(filename) as file_object:
        contents=file_object.read()
    except FileNotFoundError:
        message="Sorry,the file "+filename+" does not exist."
    print(message)
else:
    #计算文件大致包含多少个单词
    words=contents.split()
    num_words=len(words)
    print("The file "+filename+" has about "+str(num_words)+" words.")
    filenames=['alice.txt','siddhartha.txt','moby_dick.txt','little_women.txt']
    for filename in filenames:
        count_words(filename)

另一种获取异常信息的途径是通过sys模块中的exc_info()函数。该函数回返回一个三元组:(异常类，异常类的实例，跟中记录对象)

可能是您的缩进有问题，在现在看来您的缩进是有问题的。你注意缩进规则。