Question

我有一个用逗号分隔的CSV文件。我需要读取文件，确定字段（颜色）中具有特定值（例如蓝色）的字符串，并计算符合条件的字符串百分比。

到目前为止我的代码如下：

myfile = open('3517315a.csv','r')

myfilecount = 0

linecount = 0

firstline = True

for line in myfile:

       if firstline:
        firstline = False
        continue
fields = line.split(',')

    linecount += 1
    count = int(fields[0])
    colour = str(fields[1])
    channels = int(fields[2])
    code = str(fields[3])
    correct = str(fields[4])
    reading = float(fields[5])

我不知道如何设定条件并计算百分比。

Answer 1

试试这个:)它比其他答案更容易配置，并且由于csv模块，它将适用于所有类型的CSV文件。使用Python 3.6.1进行测试。

import csv
import io # needed because our file is not really a file

CSVFILE = """name,occupation,birthyear
John,Salesman,1992
James,Intern,1997
Abe,Salesman,1983
Michael,Salesman,1994"""

f = io.StringIO(CSVFILE) # needed because our file is not really a file

# This is the name of the row we want to know about
our_row = 'occupation'
# If we want to limit the output to one value, put it here.
our_value = None # For example, try 'Intern'
# This will hold the total number of rows
row_total = 0

totals = dict()

for row in csv.DictReader(f):
    v = row[our_row]
    # If we've already come across a row with this value before, add 1 to it
    if v in totals:
        totals[v] += 1
    else: # Set this row's total value to 1
        totals[v] = 1

    row_total += 1

for k, v in totals.items():
    if our_value:
        if k != our_value: continue

    print("{}: {:.2f}%".format(k, v/row_total*100))

输出：

Salesman: 75.00%
Intern: 25.00%

Answer 2

嗯，基本上有三个步骤：

获取文件中的行数。您已使用linecount
获取您的病情发生次数。让我们采用颜色：您已经提取了颜色，现在您只需将其与您要查找的值进行比较，例如：如果颜色==＆＃34;蓝色＆＃34;
计算百分比，即occurences / linecount

看起来像这样：

myfile = open('3517315a.csv','r')

myfilecount = 0

linecount = 0
occurences = 0

firstline = True

for line in myfile:

    if firstline:
        firstline = False
        continue

    fields = line.split(',')

    linecount += 1

    count = int(fields[0])
    colour = str(fields[1])
    channels = int(fields[2])
    code = str(fields[3])
    correct = str(fields[4])
    reading = float(fields[5])

    if colour == 'Blue':
        occurences_blue += 1

percentage_blue = occurences_blue / linecount

但这是一个非常基本的例子。在任何情况下，您可能应该使用Python csv库来读取csv中的字段，如对帖子（https://docs.python.org/2/library/csv.html）的评论中所建议的那样。我还希望那里有库，可以更有效地解决你的问题。

Answer 3

如果您愿意使用第三方模块，那么我强烈建议您使用Pandas。代码大致是：

import pandas as pd

df = pd.read_csv("my_data.csv")
blues = len(df[df.colour == "blue"])
percentage = blues / len(df)
print(f"{percentage}% of the colours are blue")

如何计算字段中具有特定值的字符串的百分比

3 个答案: