我一直在研究我的python技能。 这是我正在处理的数据的原始文本文件：Titanic data
每行代表一个人在船上。该文件有几列，包括该人是否幸存（第3列）。我试图计算每个人口中的人数（即男性和女性人数）以及每组幸存者的数量。
我试图分三个阶段来做这件事： 首先，添加一个与该人相关的前缀列（Mr，Mrs，Miss）。 然后，定义一个函数 - get_avg（）来标识将找到信息的列以及该列的可能值，并将它们提供给grab_values函数。 第三，grab_values（）计算每组人数和幸存者数量。
这一切都很好看而且花花公子...但它不起作用。 计数和总和我持续0。试图尽可能坚持打印命令并取得一些进展，但仍然无法理解我应该做什么。我觉得这个函数没有在所有行（或其中任何一行）上运行，但不知道这是不是真正的原因以及如何应对它。
有人可以帮忙吗？
import csv
titanic = open('shorttitanic.txt', "rb")
reader = csv.reader(titanic)
prefix_list = ["Mr ", "Mrs", "Mis"] # used to determine if passanger's name includes a prefix
# There are several demographic details we can count passengers and survivors with, this is a dictionary to map them out along with col number.
details = {"embarked":[5, "Southampton", "Cherbourg", "Queenstown", ""],
"sex":[10, "male","female"], "pclass":[1,"1st","2nd","3rd"],
"prefix":[12,"Mr ", "Mrs", "Mis"]} # first item is col number (starts at 0), other items are the possible values
# Adding another column for prefix:
rownum = 0
for row in reader:
# Finding the header:
if rownum == 0:
header = row
header.append("Prefix")
# print header
else:
prefix_location = row[3].find(",") + 2 # finds the position of the comma, the prefix starts after the comma and after a space (+2)
prefix = row[3][prefix_location:prefix_location+3] # grabs the 3 first characters of the prefix
# print len(prefix), prefix
if prefix in prefix_list: # if there's a prefix in the passanger's name, it's appended to the row
if prefix == "Mis":
row.append("Miss") # Mis is corrected to Miss on appending, since we must work with 3 chars
else:
row.append(prefix)
else:
row.append("Other/Unknown") # for cases where there's no prefix in the passanger's name
# print len(row), rownum, row[3], prefix, row[11]
# print row
rownum += 1
# grab_values() will run on all rows and count the number of passengers in each demographic and the number of survivors
def grab_values(col_num,i):
print col_num, "item name", i
count = 0
tot = 0
for row in reader:
# print type(row[col_num][0]
print row[col_num]
if row[col_num] == i:
count += 1
if row[2] == int(1):
tot += 1
# print count, tot
return count, tot
# get_avg() finds the column number and possible values of demographic x.
def get_avg(x): # x is the category (sex, embarked...)
col_num = details[x][0]
for i in details[x][1:]:
print col_num, i
# print type(i)
grab_values(col_num,i)
count,tot = grab_values(col_num,i)
print count,tot
# print i, count, tot
get_avg("sex")
titanic.close()
编辑：将字典中的前缀值更改为：“prefix”：[12，“Mr”，“Mrs”，“Mis”]}，必须完成。
EDIT2：这是完成的代码，以防任何人感兴趣。我接受了warunsl关于问题性质的建议，但是他的解决方案没有用，至少在我做出改变的时候，所以我不能选择它作为正确的解决方案以防其他人找到这个帖子并尝试从中学习。非常感谢帮助者！
import csv
titanic = open('titanic.txt', "rb")
reader = csv.reader(titanic)
prefix_list = ["Mr ", "Mrs", "Mis"] # used to determine if passanger's name includes a prefix. Using 3 chars because of Mr.
# There are several demographic details we can count passengers and survivors with, this is a dictionary to map them out along with col number.
details = {"embarked":[5, "Southampton", "Cherbourg", "Queenstown", ""],
"sex":[10, "male","female"], "pclass":[1,"1st","2nd","3rd"],
"prefix":[11,"Mr ", "Mrs", "Miss", "Unknown"]} # first item is col number (starts at 0), other items are the possible values
# try to see how the prefix values can be created by using 11 and a refernce to prefix_list
# Here we'll do 2 things:
# I - Add another column for prefix, and -
# II - Create processed_list with each of the rows in reader, since we can only run over reader once,
# and since I don't know much about handling CSVs or generator yet we'll run on the processed_list instead
processed_list = []
rownum = 0
for row in reader:
# Finding the header:
if rownum == 0:
header = row
header.append("Prefix")
else:
prefix_location = row[3].find(",") + 2 # finds the position of the comma, the prefix starts after the comma and after a space (+2)
prefix = row[3][prefix_location:prefix_location+3] # grabs the 3 first characters of the prefix
if prefix in prefix_list: # if there's a prefix in the passanger's name, it's appended to the row
if prefix == "Mis":
row.append("Miss") # Mis is corrected to Miss on appending, since we must work with 3 chars
else:
row.append(prefix)
else:
row.append("Unknown") # for cases where there's no prefix in the passanger's name
processed_list.append(row)
rownum += 1
# grab_values() will run on all rows and count the number of passengers in each demographic and the number of survivors
def grab_values(col_num,i):
# print col_num, "item name", i
num_on_board = 0
num_survived = 0
for row in processed_list:
if row[col_num] == i:
num_on_board += 1
if row[2] == "1":
num_survived += 1
return num_on_board, num_survived
# get_avg() finds the column number and possible values of demographic x.
def get_avg(x): # x is the category (sex, embarked...)
col_num = details[x][0]
for i in details[x][1:]:
print "Looking for: ", i, "at col num: ", col_num
grab_values(col_num,i)
num_on_board,num_survived = grab_values(col_num,i)
try:
proportion_survived = float(num_survived)/num_on_board
except ZeroDivisionError:
proportion_survived = "Cannot be calculated"
print "Number of %s passengers on board: " %i , num_on_board, "\n" \
"Number of %s passengers survived: " %i, num_survived, "\n" \
"Proportion of %s passengers survived: " %i, "%.2f%%" % (proportion_survived * 100), "\n"
print "Hello! I can calculate the proportion of passengers that survived according to these parameters: \n \
Embarked \n Sex \n Pclass \n Prefix", "\n"
def get_choice():
possible_choices = ["embarked","sex","pclass","prefix"]
choice = raw_input("Please enter your choice: ").lower()
if choice not in possible_choices:
print "Sorry, I can only work with Embarked / Sex / Pclass / Prefix. Please try again."
get_choice()
return choice
user_choice = get_choice()
get_avg(user_choice)
titanic.close()
答案 0 :(得分：1)
如果您阅读csv.reader的文档，您可以看到该调用返回一个实现迭代器协议的reader对象。这意味着，csv.reader函数返回了一个生成器而不是您期望的列表。
Generators元素只能使用一次。为了重用它，您必须重新初始化reader对象。这个answer对python工作中的生成器有详尽的解释。
因此，您可以在第一次读取时添加另一个列表中的所有行，然后使用此新列表，或者在再次使用之前重新初始化生成器。第二种选择是更好的方法，尤其是在您阅读大文件时：
在您grab_values前for row in reader:执行此操作：
titanic = open('titanic.txt', "rb")
reader = csv.reader(titanic)
并且您的代码有效。
编辑：由于您是在第一次阅读csv文件时修改每一行，因此您必须将修改后的行附加到新列表并使用grab_values方法中的新列表。
# Adding another column for prefix:
processed_list = [] # Declare a new array
rownum = 0
for row in reader:
if rownum == 0:
header = row
header.append("Prefix")
else:
prefix_location = row[3].find(",") + 2
prefix = row[3][prefix_location:prefix_location+3]
if prefix in prefix_list:
if prefix == "Mis":
processed_list.append("Miss") #Change this
else:
processed_list.append(prefix) #Change this
else:
processed_list.append("Other/Unknown") #Change this
在抓取值中，将for row in reader更改为for row in processed_list