在 Python3 中编辑 csv 文件

Question

您好，我对使用 python 编辑 csv 文件有点陌生。 我正在做一个项目。 这是一个简单的成绩计算器，它读取名为 new_grade.csv 的 csv 文件。 我的脚本计算每个学生的平均成绩。 我不小心硬编码了我的脚本，并且在读取多个 csv 行时遇到了问题。 我的问题是如何修改我的代码以运行任意一行数据。 我的代码只对第一行数据起作用。 任何帮助将不胜感激。

我的 .csv 文件：

Smithy, James, 100, 78, 92, 92, 85, 85, 95, 100, 75, 85, 50, 85, 87, 95, 95, 80, 80, 96, 95, 95, 95, 85, 79, 95, 85, 95, A, A+, A, B, A+, F, C, B, A, A, A, A, 85, 95, 82, 91
Gadget, John, 0, 0, 92, 92, 85, 60, 85, 100, 75, 85, 50, 85, 0, 95, 85, 70, 70, 0, 95, 95, 95, 85, 0, 95, 0, 95, F, F, F, B, A+, A, C, B, C, F, F, F, 45, 75, 82, 31
Phillips, David, 100, 78, 92, 92, 85, 90, 85, 100, 75, 85, 50, 85, 87, 95, 85, 80, 80, 96, 95, 95, 95, 85, 79, 95, 85, 95, A, A+, A, B, A+, A, A, B, C, A, A, A, 85, 95, 82, 91 

我可以解决一行数据的代码：

def main():
    try:
        import csv
        import sys
        # This section opens up the file grades.csv. It will then read the data and then takes that data and converts
        # that data into a list. When it's in a list we can splice the data to compute averages.
        with open("new_grade.csv", 'r') as f:
            list(csv.reader(f))  # had data = variable

        while True:
            # function to remove \n character from csv file
            def remove_newlines(fname):
                flist = open(fname).readlines()
                return [s.rstrip('\n') for s in flist]

            old_line = (remove_newlines("new_grade.csv"))
            # For required output:
            line = old_line[0].split(', ')  # This open up the line of the file. For instance this opens up line 1 of
            # file.
            if len(line) > 44:  # This checks to make sure that the data doesn't exceed 44 indexes
                print('The data in your file exceeds the maximum amount. Check line 1 of your file. ')
                sys.exit(1)

            def student():
                print((line[0]) + ',' + ' ' + (line[1]), end=', ')  # This finds the student's name

            def preparation_assignment_average():  # This will compute the preparation assignment average.
                global prep
                prep = 0
                for i in (line[2:16]):
                    i = int(i)
                    if 0 <= i <= 100:  # This is checking to make sure that the grades are in the range 0-100
                        prep = prep + int(i)
                    else:  # if it is not in the range of 0-100 it will print this statement and end the program
                        print('One of the values that you entered is not valid. Please enter a grade within the '
                              'range 0-100, Error\noccurred on line 1 in text file.')
                        sys.exit(1)  # This ends the program if it fails the if statement
                print(round((prep / 14), 2), end=', ')

            def lab_score_average():  # This will compute the lab score average
                global lab
                lab = 0
                for i in (line[17:28]):
                    i = int(i)
                    if 0 <= i <= 100:  # This is checking to make sure that the grades are in the range 0-100
                        lab = lab + int(i)
                    else:  # if it is not in the range of 0-100 it will print this statement and end the program
                        print('One of the values that you entered is not valid. Please enter a grade within the '
                              'range 0-100, Error\noccurred on line 1 in text file.')
                        sys.exit(1)  # This ends the program if it fails the if statement
                print(round((lab / 12), 2), end=', ')

            def post_lab_average():  # This calculates the post lab average of the student. It takes a letter and
                # converts the letter to a score that is an integer.
                global score
                score = 0
                for i in (line[28:39]):
                    if i == "A+":
                        score += 100
                    elif i == "A":
                        score += 95
                    elif i == "A-":
                        score += 90
                    elif i == "B":
                        score += 85
                    elif i == "C":
                        score += 75
                    elif i == "D":
                        score += 60
                    elif i == "F":
                        score += 0
                    elif i is not "A+" or "A" or "A-" or "B" or "C" or "D" or "F":
                        print('Your file is not formatted to the standard of the program. On line 1 of your file, '
                              'you have\na score where a letter grade should be. Please check file and rerun the '
                              'program.')
                        sys.exit(1)
                print(round((score / 12), 2), end=', ')

            def exam_average():  # This will compute the exam average for the student
                global exam
                exam = 0
                for i in (line[40:44]):
                    i = int(i)
                    if 0 <= i <= 100:  # This is checking to make sure that the grades are in the range 0-100
                        exam = exam + int(i)
                    else:  # if it is not in the range of 0-100 it will print this statement and end the program
                        print('One of the values that you entered is not valid. Please enter a grade within the '
                              'range 0-100, Error\noccurred on line 1 in text file.')
                        sys.exit(1)  # This ends the program if it fails the if statement
                print(round((exam / 4), 2), end=', ')

            def overall_weighted_class_average():  # This will compute the overall class average for the student
                global weighted_class_grade
                global weighted_prep
                global weighted_lab
                global weighted_score
                global weighted_exam
                weighted_prep = ((prep / 14) * .10)  # This is calculating the weighted average for a
                weighted_lab = ((lab / 12) * .20)  # This is calculating the weighted average for b
                weighted_score = ((score / 12) * .10)  # This is calculating the weighted average for score
                weighted_exam = ((exam / 4) * .60)  # This is calculating the weighted average for exam
                weighted_class_grade = round((weighted_prep + weighted_lab + weighted_score + weighted_exam), 2)
                print(weighted_class_grade, end=', ')

            def letter_grade_for_class():  # This will take the weighted class grade and it will print that grade
                # according to the range
                letter = weighted_class_grade
                while True:
                    if 95 < letter <= 100:
                        print("A+")
                        break
                    elif letter == 95:
                        print("A")
                        break
                    elif 90 <= letter <= 94:
                        print("A-")
                        break
                    elif 85 < letter <= 89:
                        print("B+")
                        break
                    elif letter == 85:
                        print("B")
                        break
                    elif 80 <= letter <= 84:
                        print("B-")
                        break
                    elif 75 < letter <= 79:
                        print("C+")
                        break
                    elif letter == 75:
                        print("C")
                        break
                    elif 70 <= letter <= 74:
                        print("C-")
                        break
                    elif 65 < letter <= 69:
                        print("D+")
                        break
                    elif letter == 65:
                        print("D")
                        break
                    elif 60 <= letter <= 64:
                        print("D-")
                        break
                    elif letter <= 59:
                        print("F")
                        break

            def call_functions():  # This takes all the definitions and makes it into one definition
                student()
                preparation_assignment_average()
                lab_score_average()
                post_lab_average()
                exam_average()
                overall_weighted_class_average()
                letter_grade_for_class()
                return ''

            break
        # After computing all the averages for the line of data it then writes it to a new file
        original_stdout = sys.stdout
        file = open('test_file.csv', 'x')  # The x will not save the file if it already exists
        sys.stdout = file
        for i in call_functions():
            file.writelines('\n%s' % i)
            sys.stdout = original_stdout
            file.close()
        f.close()
        
      except ValueError:  # displays when one of the letters is out of its index
        print('Sorry, one of the letters in the file is out of place. Please check the file again to make sure that \n'
              'the letter is not where the numbers are supposed to be. Check indexes 29-39. That is where the \n'
              'letter grades for the file should be.')
        sys.exit(1)
    except FileNotFoundError:  # displays error if there is no file by that name
        print("Sorry, the current file that you have selected is not a File.")
        sys.exit(1)
    except IndexError:  # this displays when there is no data in the file
        print('The file that you have selected does not contain any grades. Please check the file again.')
        sys.exit(1)
    except PermissionError:
        print('The file that you are trying to save is already a file. The file is protected and can not be written.')
        sys.exit(1)
    except FileExistsError:
        print('The file that you are trying to save is already a file. Please rename your file or delete that file '
              'and rerun the program.')
        sys.exit(1)
if __name__ == "__main__":
    main()

Answer 1

我认为有两件事可以解释您所看到的行为并暗示您可以修改代码的方式。

1. 行line = old_line[0].split(', ')表示您只读取文件的第一行。 你应该有某种循环访问文件的每一行line = old_line[index].split(',') 。

2. 以下循环可能不会执行您认为的操作：

for i in call_functions():
    file.writelines('\n%s' % i)
    sys.stdout = original_stdout
    file.close()

call_functions()方法实际上返回一个空字符串，所以这个循环的主体实际上根本不运行。 call_functions()只被调用一次，这就是你在输出 csv 中只看到一行输出的原因。 您需要为 CSV 中的每一行调用call_functions() 。

Answer 2

这是一篇冗长的文章，因此我将其分成几部分以使其更具可读性。 完整代码位于更改说明的末尾。

第一部分

我复制并粘贴了您的代码，PyCharm 和 Visual Studio 在第 72 行为您的post_lab_average()函数捕获了 SyntaxWarning 错误。

这是触发它的elif语句：

elif i is not "A+" or "A" or "A-" or "B" or "C" or "D" or "F":

该程序只是希望您更改is not !=但老实说，您在这里不需要表达式，因为您已经要检查所有其他字母。 你只需要一个else:而不是elif i != 'A+' or 'A' or ...

在进行我将要解释的所有其他更改之后，程序再次在本节中遇到问题if i == "A+":如果它检查的行中有多余的空间，则无法工作，即i = " A+" . 为了解决这个问题，我们将表达式改写为if "A+" in i:这允许我们检查"A+"无论是否有额外的空格。

你的post_lab_average()应该是这样的：

def post_lab_average():

    global score
    score = 0
    for i in (line[28:39]):
        if "A+" in i:
            score += 100
        elif "A" in i:
            score += 95
        elif "A-" in i:
            score += 90
        elif "B" in i:
            score += 85
        elif "C" in i:
            score += 75
        elif "D" in i:
            score += 60
        elif "F" in i:
            score += 0
        else:
            print('Your file is not formatted to the standard of the program. On line 1 of your file, '
                  'you have\na score where a letter grade should be. Please check file and rerun the '
                  'program.')
            exit(1)

此外，在整个代码中，您调用sys.exit(1)来终止程序sys.exit(1) sys. 是不必要的，只使用exit(1)就可以了。

第二部分

弹出的下一个错误是该行的异常FileExistsError

file = open('test_file.csv', 'x')

最后，我们会将数据附加到 csv 文件，因此我们将在main()函数的开头包含这行代码：

import os

try:
    os.remove('test_file.csv')
except FileNotFoundError:
    pass

如果文件存在，这将始终删除该文件，并且您可以在最后删除您的except FileExistsError:因为异常将不再触发。

第三部分

使用with open()打开文件时，默认设置是读取文件，因此您不需要添加'r'您实际上不需要函数remove_newlines() ，我们将打开文件并分配数据到像这样的列表：

with open('new_grade.csv') as file:
    student_list = list(csv.reader(file))

第四部分

现在我们将调整您的while True循环以使用计数器运行，当它运行完所有列表时停止。

count = 0
while count < len(student_list):
    line = student_list[count]
    count += 1

循环将继续，直到遍历student_list所有子列表。 您必须在循环结束时摆脱break才能使其正常工作。

第五部分

快完成了！ 在当前状态下运行文件将生成一个文件，其中只有最后一个学生的条目。 为了解决这个问题，我们将缩进写入文件的代码块，以便它在每个循环结束时运行，而不是在循环结束后运行。 我还重新格式化以with open('a')一起使用with open('a')这样我们就可以附加我们的数据而不是覆盖。

original_stdout = sys.stdout
with open('test_file.csv', 'a') as file:
    sys.stdout = file
    for i in call_functions():
        file.writelines('\n%s' % i)
        sys.stdout = original_stdout

最终代码

def main():
    try:
        import csv
        import sys
        import os

        # Checks if file exists and removes it if found
        try:
            os.remove('test_file.csv')
        except FileNotFoundError:
            pass

        # Opens the data file and assigns it to a list
        with open('new_grade.csv') as file:
            student_list = list(csv.reader(file))

        # Loops through each student in list
        count = 0
        while count < len(student_list):
            line = student_list[count]
            count += 1

            if len(line) > 44:  # This checks to make sure that the data doesn't exceed 44 indexes
                print('The data in your file exceeds the maximum amount. Check line 1 of your file. ')
                sys.exit(1)

            def student():
                print((line[0]) + ',' + ' ' + (line[1]), end=', ')  # This finds the student's name

            def preparation_assignment_average():  # This will compute the preparation assignment average.
                global prep
                prep = 0
                for i in (line[2:16]):
                    i = int(i)
                    if 0 <= i <= 100:  # This is checking to make sure that the grades are in the range 0-100
                        prep = prep + int(i)
                    else:  # if it is not in the range of 0-100 it will print this statement and end the program
                        print('One of the values that you entered is not valid. Please enter a grade within the '
                              'range 0-100, Error\noccurred on line 1 in text file.')
                        exit(1)  # This ends the program if it fails the if statement
                print(round((prep / 14), 2), end=', ')

            def lab_score_average():  # This will compute the lab score average
                global lab
                lab = 0
                for i in (line[17:28]):
                    i = int(i)
                    if 0 <= i <= 100:  # This is checking to make sure that the grades are in the range 0-100
                        lab = lab + int(i)
                    else:  # if it is not in the range of 0-100 it will print this statement and end the program
                        print('One of the values that you entered is not valid. Please enter a grade within the '
                              'range 0-100, Error\noccurred on line 1 in text file.')
                        exit(1)  # This ends the program if it fails the if statement
                print(round((lab / 12), 2), end=', ')

            def post_lab_average():  # This calculates the post lab average of the student. It takes a letter and
                # converts the letter to a score that is an integer.
                global score
                score = 0
                for i in (line[28:39]):
                    if "A+" in i:
                        score += 100
                    elif "A" in i:
                        score += 95
                    elif "A-" in i:
                        score += 90
                    elif "B" in i:
                        score += 85
                    elif "C" in i:
                        score += 75
                    elif "D" in i:
                        score += 60
                    elif "F" in i:
                        score += 0
                    else:
                        print('Your file is not formatted to the standard of the program. On line 1 of your file, '
                              'you have\na score where a letter grade should be. Please check file and rerun the '
                              'program.')
                        exit(1)
                print(round((score / 12), 2), end=', ')

            def exam_average():  # This will compute the exam average for the student
                global exam
                exam = 0
                for i in (line[40:44]):
                    i = int(i)
                    if 0 <= i <= 100:  # This is checking to make sure that the grades are in the range 0-100
                        exam = exam + int(i)
                    else:  # if it is not in the range of 0-100 it will print this statement and end the program
                        print('One of the values that you entered is not valid. Please enter a grade within the '
                              'range 0-100, Error\noccurred on line 1 in text file.')
                        exit(1)  # This ends the program if it fails the if statement
                print(round((exam / 4), 2), end=', ')

            def overall_weighted_class_average():  # This will compute the overall class average for the student
                global weighted_class_grade
                global weighted_prep
                global weighted_lab
                global weighted_score
                global weighted_exam
                weighted_prep = ((prep / 14) * .10)  # This is calculating the weighted average for a
                weighted_lab = ((lab / 12) * .20)  # This is calculating the weighted average for b
                weighted_score = ((score / 12) * .10)  # This is calculating the weighted average for score
                weighted_exam = ((exam / 4) * .60)  # This is calculating the weighted average for exam
                weighted_class_grade = round((weighted_prep + weighted_lab + weighted_score + weighted_exam), 2)
                print(weighted_class_grade, end=', ')

            def letter_grade_for_class():  # This will take the weighted class grade and it will print that grade
                # according to the range
                letter = weighted_class_grade
                while True:
                    if 95 < letter <= 100:
                        print("A+")
                        break
                    elif letter == 95:
                        print("A")
                        break
                    elif 90 <= letter <= 94:
                        print("A-")
                        break
                    elif 85 < letter <= 89:
                        print("B+")
                        break
                    elif letter == 85:
                        print("B")
                        break
                    elif 80 <= letter <= 84:
                        print("B-")
                        break
                    elif 75 < letter <= 79:
                        print("C+")
                        break
                    elif letter == 75:
                        print("C")
                        break
                    elif 70 <= letter <= 74:
                        print("C-")
                        break
                    elif 65 < letter <= 69:
                        print("D+")
                        break
                    elif letter == 65:
                        print("D")
                        break
                    elif 60 <= letter <= 64:
                        print("D-")
                        break
                    elif letter <= 59:
                        print("F")
                        break

            def call_functions():  # This takes all the definitions and makes it into one definition
                student()
                preparation_assignment_average()
                lab_score_average()
                post_lab_average()
                exam_average()
                overall_weighted_class_average()
                letter_grade_for_class()
                return ''

            # After computing all the averages for the line of data it then writes it to a new file
            original_stdout = sys.stdout
            with open('test_file.csv', 'a') as file:
                sys.stdout = file
                for i in call_functions():
                    file.writelines('\n%s' % i)
                    sys.stdout = original_stdout

    except ValueError:  # displays when one of the letters is out of its index
        print('Sorry, one of the letters in the file is out of place. Please check the file again to make sure that \n'
              'the letter is not where the numbers are supposed to be. Check indexes 29-39. That is where the \n'
              'letter grades for the file should be.')
        exit(1)
    except FileNotFoundError:  # displays error if there is no file by that name
        print("Sorry, the current file that you have selected is not a File.")
        exit(1)
    except IndexError:  # this displays when there is no data in the file
        print('The file that you have selected does not contain any grades. Please check the file again.')
        exit(1)
    except PermissionError:  # this displays when you have the file open
        print('The file that you are trying to open is already open. Close the file and restart the program.')
        exit(1)


if __name__ == "__main__":
    main()