if_stmt ::="if"expression":"suite ("elif"expression":"suite)* ["else"":"suite] It selects exactly one of the suites by evaluating the expressions one by one until one is found to betrue; then that suite is executed 注意上面加粗的地方true, 很明显 if 后面表达式预期值应该为true或者fals...
Another way which also works but is not necessary is to check if the length is equal to 0:if len(my_list) == 0: print("List is empty") Although the first approach is considered to be more Pythonic, some people prefer the explicit second approach....
To check if NumPy array is empty in Python, we can use some functions like the size() function will provide the number of elements in the array, any() provides boolean values if any True value is present inside the array, shape() provides the dimension of the array, and tolist() will...
'''ifobjisNone:returnTrueifisinstance(obj,(list,tuple,str)):returnlen(obj)==0ifisinstance(obj,dict):returnlen(obj.keys())==0returnFalse 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 从上面的代码可以看出,empty函数接受一个参数obj,并根据不同的对象类型进行判断。如果对...
1. 使用if语句判断参数是否为None 在Python中,None表示空值。我们可以使用if语句判断参数是否为None,示例代码如下: defcheck_none(param):ifparamisNone:print("参数为空")else:print("参数不为空")check_none(None)# 参数为空check_none("example")# 参数不为空 ...
__init__(self): self.attribute = None # 创建对象实例 obj = MyClass() # 检查属性是否为None attr_name = "attribute" attr_value = getattr(obj, attr_name) if attr_value is None: print(f"The attribute '{attr_name}' is None.") else: print(f"The attribute '{attr_name}' is not ...
「练习 2.3」调用自定义函数 is_empty,它接受一个参数并检查它是否为空 代码语言:javascript 复制 defis_empty(obj):# 因为题目中未指明具体类型,所以仅举例几个类型做为判断,实际的应用一般都会预期的类型iftype(obj)is str:returnobj==''eliftype(obj)==list:returnlen(obj)==0eliftype(...
Peking University is set up at 1898. 样例输出 4 33.2、我的代码 s=input() total=0 for i in s: if i>='0' and i<='9': total+=1 print(total) 034:大小写字母互换 34.1、题目 描述 把一个字符串中所有出现的大写字母都替换成小写字母,同时把小写字母替换成大写字母。 输入输入一行:待互换的...
如果您在计算机上使用的是 Mac OS X 或 Linux 安装,可能已经预先安装了 Python 解释器。要查看是否已安装,请打开终端并输入python。您可能会看到类似以下内容: $ python Python2.7.6(default, Mar222014,22:59:56) [GCC4.8.2] on linux2Type"help","copyright","credits"or"license"formore ...
To check if a key resides within the dictionary: if 'Helium' in elements: print('Helium is present') 5. Iterating Over Keys To iterate over the keys in the dictionary: for element in elements: print(element) # Prints each key 6. Iterating Over Values To traverse through the values in...