python - 在 'for' 循环期间创建并写入新的 csv 文件

Question

下面的代码旨在创建一个名为“file-0.csv”的 csv 文件，并通过迭代 for 循环开始写入行，直到达到 100 行。当达到限制时，它应该停止写入“file-0.csv”，创建“file-1.csv”，并在停止处继续 for 循环，开始写入“file-1.csv” -1.csv' 直到达到 100 行，依此类推，直到 for 循环完成。

下面代码的实际行为(完整且可执行)是它按预期创建新文件(总共 4 个)，但它继续将所有行写入“file-0”....

##### Python 3.5 #####

import csv

rowCounter     = 0
fileCounter    = 0
List_A         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_B         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_C         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']


def new_file():
    global fileCounter
    fileCounter += 1
    with open('file-' + str(fileCounter) + '.csv', 'w') as csvfile:
        rowWriter = csv.writer(csvfile, delimiter=',', quoting=csv.QUOTE_NONE)

with open('file-' + str(fileCounter) + '.csv', 'w') as csvfile:
    rowWriter = csv.writer(csvfile, delimiter=',', quoting=csv.QUOTE_NONE)

    for word1 in List_A:
        for word2 in List_B:
            for word3 in List_C:
                sentence = word1 + word2 + word3
                rowWriter.writerow ([sentence])

                rowCounter += 1

                if rowCounter == 100:
                    new_file()
                    rowCounter = 0
                else:
                    continue

与上面相同的代码，但有大量注释:

##### Python 3.5 #####

######################
####### Setup ########
######################

### Use the CSV library
import csv

### Initialize counters
rowCounter     = 0
fileCounter    = 0

### Create three lists of 'words'
List_A         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_B         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_C         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']

### Function/subroutine that creates new CSV file with incremented filename
def new_file():
    ### Make the variable 'fileCounter' usable by the function
    global fileCounter
    ### Add 1 to 'fileCounter'
    fileCounter += 1
    ### Create new CSV file using the value of 'fileCounter' as part of the name
    with open('file-' + str(fileCounter) + '.csv', 'w') as csvfile:
        rowWriter = csv.writer(csvfile, delimiter=',', quoting=csv.QUOTE_NONE)


######################
#### Main Program ####
######################

### Create initial CSV file using the value of 'fileCounter' as part of the name
with open('file-' + str(fileCounter) + '.csv', 'w') as csvfile:
    ### Create writer object and define how it should behave
    rowWriter = csv.writer(csvfile, delimiter=',', quoting=csv.QUOTE_NONE)

    ### Create & Write lines ###
    ### Nested 'for' loops to iterate through all combinations of words
    for word1 in List_A:
        for word2 in List_B:
            for word3 in List_C:
                ### Build our 'sentence' from the current iteration
                sentence = word1 + word2 + word3
                ### Write 'sentence' to file
                rowWriter.writerow ([sentence])

                ### Increment row counter
                rowCounter += 1

                ### Check if value of rowCounter is 100 and if so, execute
                ### 'new_file' and reset rowCounter to 0. If not, continue.
                if rowCounter == 100:
                    new_file()
                    rowCounter = 0
                else:
                    continue

我怀疑问题是“rowWriter”没有得到更新或正确传递回主循环，但我似乎不知道如何做到这一点(无论如何，我什至不确定是否就是这样) .

我尝试记录并使代码“通用”，以便其他人可以从任何答案中得到一些用途。非常感谢任何帮助。

Answer 1

离开with block 将关闭文件。因此，new_file 函数只是打开并立即关闭文件。

您可以执行以下操作:

import csv

rowCounter     = 0
fileCounter    = 0
List_A         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_B         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_C         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']

# create file handle
csvfile = open('file-' + str(fileCounter) + '.csv', 'w')

rowWriter = csv.writer(csvfile, delimiter=',', quoting=csv.QUOTE_NONE)

for word1 in List_A:
    for word2 in List_B:
        for word3 in List_C:
            sentence = word1 + word2 + word3
            rowWriter.writerow ([sentence])

            rowCounter += 1

            if rowCounter == 100:
                # close current filehandle
                csvfile.close()
                fileCounter += 1
                # open new file
                csvfile =  open('file-' + str(fileCounter) + '.csv', 'w')
                rowWriter = csv.writer(csvfile, delimiter=',', quoting=csv.QUOTE_NONE)
                rowCounter = 0

# close file
csvfile.close()

或者定义一个函数:

import csv

rowCounter     = 0
fileCounter    = 0
List_A         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_B         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
List_C         = ['a', 'b', 'c', 'd', 'e', 'f', 'g']

def new_writer( csvfile, counter ):
     if csvfile: 
         csvfile.close()

     # open new file
     csvfile =  open('file-' + str(counter) + '.csv', 'w')
     rowWriter = csv.writer(csvfile, delimiter=',', quoting=csv.QUOTE_NONE)

     counter += 1

     return rowWriter,csvfile,counter

rowWriter, csvFile, fileCounter = new_writer( None, fileCounter )

for word1 in List_A:
    for word2 in List_B:
        for word3 in List_C:
            sentence = word1 + word2 + word3
            rowWriter.writerow ([sentence])

            rowCounter += 1

            if rowCounter == 100:
                # close current file and open a new one
                rowWriter, csvfile, counter =  new_writer( csvfile, fileCounter )         
                rowCounter = 0

# close file
csvFile.close()