Python|检查字符串是否只包含数字

给定一个字符串，编写一个Python程序来判断一个字符串是否只包含数字。让我们看看解决上述任务的几种方法。
方法 #1：使用 isdigit() 方法

Python3

# Python3 code to demonstrate
# how to check whether string contains
# only numbers or not
 
# Initialising string
ini_string1 = '1234556'
ini_string2 = 'ab123bc'
 
# printing initial string
print ("Initial Strings : ", ini_string1, ini_string2)
 
# Using isdigit()
if ini_string1.isdigit():
    print ("String1 contains all numbers")
else:
    print ("String1 doesn't contains all numbers")
     
if ini_string2.isdigit():
    print ("String2 contains all numbers")
else:
    print ("String2 doesn't contains all numbers")

输出：

Initial Strings :  1234556 ab123bc
String1 contains all numbers
String2 doesn't contains all numbers

方法#2：使用正则表达式

Python3

# Python3 code to demonstrate
# how to check whether string contains
# only numbers or not
import re
 
# Initialising string
ini_string1 = '1234556'
ini_string2 = 'ab123bc'
 
# printing initial string
print ("Initial Strings : ", ini_string1, ini_string2)
 
# Using regex()
if re.match('^[0-9]*$', ini_string1):
    print ("String1 contains all numbers")
else:
    print ("String1 doesn't contains all numbers")
     
if re.match('^[0-9]*$', ini_string2):
    print ("String2 contains all numbers")
else:
    print ("String2 doesn't contains all numbers")

输出：

Initial Strings :  1234556 ab123bc
String1 contains all numbers
String2 doesn't contains all numbers

方法#3：使用尝试/异常

Python3

# Python3 code to demonstrate
# how to check whether string contains
# only numbers or not
 
# Initialising string
ini_string1 = '1234556'
ini_string2 = 'abc123'
 
# printing initial string
print ("Initial Strings : ", ini_string1, ini_string2)
 
# Using try / exception:
try:
    num = int(ini_string1)
    print ("String1 contains only digits")
except:
    print ("String1 doesn'tcontains only digits")
     
try:
    num = int(ini_string2)
    print ("String2 contains only digits")
except:
    print ("String2 doesn't contains only digits")
    

输出：

Initial Strings :  1234556 abc123
String1 contains only digits
String2 doesn't contains only digits