如何在CSV读取器找到第一个符合条件的数据后终止循环？

现有代码遍历CSV文件时，内层循环找到电话号码后只会跳出当前内层循环，外层的行遍历会继续执行，导致输出所有匹配的电话号码。需求是找到第一个符合条件的号码后立即停止所有循环。

现有代码 #

import csv as cs  # 假设已导入csv模块

def isPhoneNumber(text):
    # 假设这是已实现的电话号码判断函数
    return len(text) == 12 and text.count('-') == 2

with open("ten.csv", 'rb') as f:
    reader = cs.DictReader(f)
    
    for row in reader:
        for i in range(len(list_of_column_names[0])):
            if isPhoneNumber(str(row[list_of_column_names[0][i]])) == True:
                print(row[list_of_column_names[0][i]])
                break

对应CSV数据 #

id,first_name,last_name,email,gender,dob,street,city,zip,state,drivers_license,phone,userid,ssn
1,Nanon,le Keux,nlekeux0@mlb.com,Female,4/25/2020,0 Blaine Trail,Charlotte,11111,NC,646144685,704-435-8128,1111122,123-45-6789
2,Brewster,Dagnall,bdagnall1@usnews.com,Male,2/27/2014,8 Farwell Point,Montgomery,11111,AL,146790405,334-133-5888,1111122,234-56-7890
3,Eirena,Whyborne,ewhyborne2@usda.gov,Female,9/16/1996,2120 Dexter Court,Washington,11111,DC,6732768794,202-558-7854,1111122,345-67-8901
4,Kippy,Sterndale,ksterndale3@bloglovin.com,Male,7/19/1965,61 Northwestern Place,Naples,11111,FL,7202285517,941-380-3634,1111122,456-78-9012
5,Creigh,Bleckly,cbleckly4@bloomberg.com,Male,10/29/1997,63151 Prairie Rose Circle,Tampa,11111,FL,9060794486,813-210-7870,1111122,567-89-0123
6,Caleb,Feldbaum,cfeldbaum5@springer.com,Male,10/23/1962,738 American Ash Park,Birmingham,11111,AL,5049418992,205-767-9467,1111122,678-90-1234
7,Luisa,Reeder,lreeder6@google.es,Female,9/3/2014,81399 Karstens Pass,Miami,11111,FL,3476652874,305-531-4287,1111122,789-01-2345
8,Bondon,Copper,bcopper7@census.gov,Male,1/9/1975,4439 Goodland Circle,Cincinnati,11111,OH,9573026686,513-966-8317,1111122,890-12-2344
9,Hedi,Aleksankov,haleksankov8@is.gd,Female,4/24/2021,4 Union Drive,Green Bay,11111,WI,5202059280,920-509-9672,1111122,901-23-4567
10,Uriah,Dunphie,udunphie9@hubpages.com,Male,2/4/2010,73 Hagan Hill,Bronx,11111,NY,8393306353,718-578-5726,1111122,012-34-5678

解决方案 #

方法1：使用标志变量 #

设置布尔变量标记是否找到目标，找到后修改标记，在外层循环中判断标记并跳出。同时优化列遍历逻辑，直接遍历列名而非索引，代码更简洁：

import csv as cs

def isPhoneNumber(text):
    return len(text) == 12 and text.count('-') == 2

list_of_column_names = [['phone']]  # 假设这里是目标列名列表

found = False
with open("ten.csv", 'rb') as f:
    reader = cs.DictReader(f)
    
    for row in reader:
        if found:
            break
        for col in list_of_column_names[0]:
            value = str(row[col])
            if isPhoneNumber(value):
                print(value)
                found = True
                break

方法2：用函数封装，利用return终止 #

把读取逻辑放到函数里，找到匹配项后直接return，自然终止所有循环：

import csv as cs

def isPhoneNumber(text):
    return len(text) == 12 and text.count('-') == 2

list_of_column_names = [['phone']]

def find_first_phone():
    with open("ten.csv", 'rb') as f:
        reader = cs.DictReader(f)
        
        for row in reader:
            for col in list_of_column_names[0]:
                value = str(row[col])
                if isPhoneNumber(value):
                    print(value)
                    return  # 直接返回，终止所有循环

find_first_phone()

方法3：利用Python的for-else结构 #

外层循环的else块会在循环正常结束（未被break打断）时执行，内层找到匹配后，先break内层，再break外层：

import csv as cs

def isPhoneNumber(text):
    return len(text) == 12 and text.count('-') == 2

list_of_column_names = [['phone']]

with open("ten.csv", 'rb') as f:
    reader = cs.DictReader(f)
    
    for row in reader:
        for col in list_of_column_names[0]:
            value = str(row[col])
            if isPhoneNumber(value):
                print(value)
                break
        else:
            continue  # 内层循环没break，继续下一行
        break  # 内层循环break了，跳出外层循环

内容的提问来源于stack exchange，提问作者tlowa