如果用户输入字符串为空或数字或具有非 ascii-Python

Question

当用户输入名字时，如果它是空白的或者有数字或字母数字或者有非 ascii 字符，我不会将它插入数据库。

下面这段代码不接受有效输入，只有当我使用 len 和 isDigit 这两个条件时它才有效。

while (len(f_name) == 0  or f_name.isdigit()

或

f_name.encode('ascii',errors='ignore') or f_name.isalnum()):

Create new user: Y/N ?y
Enter first name: ui
First name cannot be empty or have numeric values

有人可以解释一下如何解决这个问题吗？谢谢你的时间。其余代码如下：

import sqlite3

#connect a built in function to connect or create db
conn=sqlite3.connect('phonebook.db')

#Create a cursor function which allows us to do sql operations
crsr=conn.cursor()

#This function to check if table exists
def create_Table():
    #Check if the table exists or not
    crsr.execute("SELECT name FROM sqlite_master WHERE name='phonebook'")
    tableSize=len(crsr.fetchall())#will be greater than 0 if table exists
    if tableSize>0:
        print()
    else:
        #create the table
        crsr.execute(""" Create Table phonebook(
                    FirstName text NOT NULL,
                    LastName text,
                    Phone text PRIMARY KEY NOT NULL)
                   """)

        #check if table got created or not
        crsr.execute("SELECT name FROM sqlite_master WHERE name='phonebook'")
        tableSize = len(crsr.fetchall())  # will be greater than 0 if table exists
        if tableSize > 0:
            print('Table was created successfully')

#This function will create new users and insert in DB
def create_User():
    try:
        while True:
            rsp = input('Create new user: Y/N ?')
            if rsp == 'y':
                f_name = input('Enter first name: ')
                # First name cannot be empty or have numeric values
                while (len(f_name) == 0  or f_name.isdigit() or f_name.encode('ascii',errors='ignore') or f_name.isalnum()):
                    print('First name cannot be empty or have numeric values')
                    f_name = input('Enter first name: ')
                l_name = input('Enter last name: ')
                phone = input('Enter phone number: ')
                crsr.execute("INSERT INTO phonebook VALUES (:FirstName, :LastName, :Phone)",
                             {'FirstName': f_name, 'LastName': l_name, 'Phone': phone})
                conn.commit()
            if rsp == 'n':
                break
    except:
     print('UNIQUE constraint failed: phone number already exists')

Answer 1

使用isalpha确保字符串只有字母：

f_name = input('Enter first name: ')
if f_name and f_name.isalpha():
  # your ACCEPTED logic here

此外，如果您需要检查这些字母是否为 ASCII，您可以将它们的编码长度与其自身进行比较：

f_name = input('Enter first name: ')
if f_name and f_name.isalpha() and len(f_name) == len(f_name.encode()):
  # your ACCEPTED logic here

编辑添加了空字符串检查（即 if f_name）

Answer 2

如果您熟悉正则表达式，可以按以下方式测试条件 "must not be empty" 和 "must not contain digits"：

import re

# match one or more characters that range from a to z or A to Z
username_check = re.compile(r'[a-zA-Z]+')

...
while True:
  if rsp == 'y':
    f_name = input('Enter first name: ')
    while not username_check.fullmatch(f_name):
      print('First name cannot be empty or have numeric values')
      f_name = input('Enter first name: ')

正则表达式的好处在于您可以非常灵活地扩展当前的最小解决方案以测试非常具体的模式：

import re

# allow unicode word characters
allowed = re.compile(r'\w+')
# numbers are still not allowed
forbidden = re.compile(r'\d')

while True:
    f_name = input('Enter first name: ')
    while not (allowed.fullmatch(f_name) and not forbidden.search(f_name)):
      print('First name cannot be empty or have numeric values')
      f_name = input('Enter first name: ')

如果用户输入字符串为空或数字或具有非 ascii-Python

If userinput String is empty or numeric or has non ascii-Python

python

string

alphanumeric