Question

我对python很新，遇到了一个我认为很奇怪的问题。我正在搜索csvfile的第一列。

我正在使用csv模块并且有一些嵌套for循环的代码。我的意图是每次找到匹配时，中间的循环从csvfile的第一行重新启动。但它总是从csv中搜索的最后一行开始。

下面的代码和结果将使我的问题更加明显。

number = [1,3,5,6,7,8,1234,324,5,2,35]

import csv

with open('...../Documents/pycharm/testcsv.csv', 'rb') as csvimport:
    csvfile = csv.reader(csvimport)

    for num in number:
        print 'looking for ' + str(num)
        is_in_file = False
        print 'set to false'
        for row in csvfile:
            print 'looking at value ' + row[0]
            if row[0] == str(num):
                is_in_file = True
                print 'match, set to true'
                break
        print 'test1'
        if is_in_file == False:
            print str(num) + ' not found in file!'

以下是在IDE中打印的内容：

looking for 1
set to false
looking at value a
looking at value 1
match, set to true
test1
looking for 3
set to false

注意：这里我想看一下csvfile的第一行（值a）。相反，它会查看csvfile的第三行（值＆＃39;＆＃39;）。

looking at value 
looking at value 1234
looking at value 7
looking at value 1
looking at value 3
match, set to true
test1

从现在开始，它一直跳过我的内部循环，因为它已经通过了最后一行：

looking for 5
set to false
looking at value 5
match, set to true
test1
looking for 6
set to false
looking at value 6
match, set to true
test1
looking for 7
set to false
looking at value 77
looking at value 23
looking at value 87
test1
7 not found in file!
looking for 8
set to false
test1
8 not found in file!
looking for 1234
set to false
test1
1234 not found in file!
looking for 324
set to false
test1
324 not found in file!
looking for 5
set to false
test1
5 not found in file!
looking for 2
set to false
test1
2 not found in file!
looking for 35
set to false
test1
35 not found in file!

这是csvfile

a,c,b,d,e
1,3,4,5,6
,7,7,,87
1234,1,98,7,76
7,8,90,0,8
1,3,98,0,0
3,cat,food,20,39
5,%,3,6,90
6,2,2,2,3
77,3,4,3,5
23,3,4,3,6
87,5,5,5,

Answer 1

csvfile是一个生成器：第一次它会工作，但第二次它会立即返回。考虑这样做：

csvfile = list(csv.reader(csvimport))

然后，您可以根据需要扫描csvfile。

但是，当您对文件执行线性扫描时，此代码的效果并不高。考虑改为做字典。这是

的方式

d = dict()
for r in csvfile:
    d[r[0]] = r[1:]

然后，用：

替换你的内循环

if num in d:
   is_in_file = True
   print("%d is in file" % num)

Python CSV搜索

1 个答案: