Python函数名中允许使用哪些字符？

赋予函数或变量的用户定义名称称为标识符。它有助于区分一个实体和另一个实体，有时还可以定义该实体的使用。与每种编程语言一样，标识符也有一些限制/限制。因此，对于Python来说，在使用标识符之前，我们需要注意以下几点。

编写标识符的规则：

第一个也是最重要的限制是标识符不能与关键字相同。每种编程语言中都有特殊的保留关键字，它们有自己的含义，这些名称不能用作Python中的标识符。

Python3

# Python program to demonstrate
# that keywords cant be used as
# identifiers
 
def calculate_sum(a, b):
  return a + b
 
x = 2
y = 5
print(calculate_sum(x,y))
 
# def and if is a keyword, so
# this would give invalid
# syntax error
def = 12  
if = 2     
 
print(calculate_sum(def, if))

Python3

# Python code to demonstrate
# that we can't use special
# character like !,@,#,$,%.etc
# as identifier
 
# valid identifier
var1 = 46 
var2 = 23 
print(var1 * var2)
 
# invalid identifier,
# will give invalid syntax error
var@ = 12 
$var = 55 
print(var@ * $var)
 
# even function names can't
# have special characters
def my_function%():
  print('This is a function with invalid identifier')
   
my_function%()

Python3

# Python program to demonstrate
# some examples of valid identifiers
 
var1 = 101
ABC = "This is a string"
fr12 = 20
x_y = 'GfG'
slp__72 = ' QWERTY'
 
print(var1 * fr12)
 
print(ABC + slp__72)

输出：

File "/home/9efd6943df820475cf5bc74fc4fcc3aa.py", line 15
    def = 12   
        ^
SyntaxError: invalid syntax

Python中的标识符不能使用任何特殊符号，如 !、@、#、$、% 等。

Python3

# Python code to demonstrate
# that we can't use special
# character like !,@,#,$,%.etc
# as identifier
 
# valid identifier
var1 = 46 
var2 = 23 
print(var1 * var2)
 
# invalid identifier,
# will give invalid syntax error
var@ = 12 
$var = 55 
print(var@ * $var)
 
# even function names can't
# have special characters
def my_function%():
  print('This is a function with invalid identifier')
   
my_function%()

输出：

File "/home/3ae3b1299ee9c1c04566e45e98b13791.py", line 13
    var@ = 12  
         ^
SyntaxError: invalid syntax

除了这些限制之外， Python还允许标识符是小写字母（a 到 z）或大写字母（A 到 Z）或数字（0 到 9）或下划线 (_) 的组合。但变量名不能以数字开头。 myClass、var_3 和 print_to_screen 等名称都是有效的示例。

Python3

# Python program to demonstrate
# some examples of valid identifiers
 
var1 = 101
ABC = "This is a string"
fr12 = 20
x_y = 'GfG'
slp__72 = ' QWERTY'
 
print(var1 * fr12)
 
print(ABC + slp__72)

输出：

2020
This is a string QWERTY