如何在打印项目之前计算 CSV 中的行数？

Question

with open("C:/Users/number-UK.csv") as csvfile:
    # read csv
    readCSV = csv.reader(csvfile, delimiter=',')

    # print the number of items/rows in the csv file
    print("Step 2: Confirm the total numbers:",int(len(list(readCSV)))-1)   
    continue_text = input("Enter anything to continue")

    # skip the headers
    next(readCSV, None)  

    i=0
    for each_user in readCSV:
        print(i+1," item:",str(each_user[0]))
        i = i + 1

print("all done!")

上面的代码不起作用。当我删除下面的行时，代码就可以工作了。

print("Step 2: Confirm the total numbers:",int(len(list(readCSV)))-1)

我想在for循环之前计算csv文件的行数，有人知道如何实现这一点吗？非常感谢。

Answer 1

问题是“list(readCSV)”耗尽了读者的精力，因此您的后续调用不再有任何元素。

两种补救方法。

选项 1（使用列表而不是生成器进行 readCSV）

with open("C:/Users/number-UK.csv") as csvfile:
    # read csv (using list rather than iterator)
    readCSV = list(csv.reader(csvfile, delimiter=','))

    # print the number of items/rows in the csv file
    print("Step 2: Confirm the total numbers:",int(len(readCSV))-1)   
    continue_text = input("Enter anything to continue")

    # skip the headers
    #next(readCSV, None)  # not used

    i=0
    for each_user in readCSV[1:]:  # start at 1 to skip header
        print(i+1," item:",str(each_user[0]))
        i = i + 1

print("all done!")

选项2（重新获取readCSV）

with open("C:/Users/number-UK.csv") as csvfile:
    # read csv
    readCSV = csv.reader(csvfile, delimiter=',')

    # print the number of items/rows in the csv file
    print("Step 2: Confirm the total numbers:",int(len(readCSV))-1)   
    continue_text = input("Enter anything to continue")

    # Reacquire (i.e. reset) readCSV iterator
    readCSV = csv.reader(csvfile, delimiter=',')

    # skip the headers
    next(readCSV, None)  # not used

    i=0
    for each_user in readCSV[1:]:  # start at 1 to skip header
        print(i+1," item:",str(each_user[0]))
        i = i + 1

print("all done!")

选项 3（使用枚举为）

根据snakecharmerb的建议

 with open("C:/Users/number-UK.csv") as csvfile:
    # read csv (using list rather than iterator)
    readCSV = list(csv.reader(csvfile, delimiter=','))

    # print the number of items/rows in the csv file
    print("Step 2: Confirm the total numbers:",int(len(readCSV))-1)   
    continue_text = input("Enter anything to continue")

    # skip the headers
    #next(readCSV, None)  # not used (header skipped by using readCSV[1:])

    for i, each_user in enumerate(readCSV[1:], start = 1):# start readCSV at 1 
                                               # to skip header
        print(i," item:",str(each_user[0]))  # i starts at 1, 
                                             # so no need to increment

print("all done!")

Answer 2

解决方法是将 csv 加载到 pandas 数据框中并测量其大小。

import pandas as pd
test = pd.read_csv('data.csv')
print(len(test))

您现在可以找到 for 循环之前的行数。

Answer 3

你可以这样做：

count = len(csvfile.readlines()))
f.seek(0)

count

将保存文件中的行数。 注意执行

f.seek(0)

将文件读取指针移动到文件的开头，否则您将无法读取其他任何内容，因为

readlines()

会一直读取到文件末尾。