In Python, all the iterable objects like strings, lists, and tuples evaluate to False when they are empty. Therefore, an empty string evaluates to False. To check if a string is empty or whitespace using the not operator, we will use the not operator on the input string. If the strin...
The __eq__() is an elegant way to check. len() function is used to get the length of the string and check if it is 0 to get if a string is empty.String Empty Check ExpressionResult if not test_str: True when a string is empty.False when a string has a value. if test_str:...
# None, 0, and empty strings/lists/dicts/tuples all evaluate to False.# All other values are Truebool(None)# => Falsebool(0)# => Falsebool("")# => Falsebool([])# => Falsebool({})# => Falsebool(())# => False 除了上面这些值以外的所有值传入都会得到True。 变量与集合 输入输出...
所有类型的默认空值会被返回False,否则都是True。比如0,“”,[], {}, ()等。 # None, 0, and empty strings/lists/dicts/tuples all evaluate to False. # All other values are True bool(None)# => False bool() # => False bool("") # => False bool([]) # => False bool({}) # =...
特殊常量 True 和 False 是“布尔”类型。特殊常量 None 是“NoneType”。 要查看任何对象的文本定义,可以使用 str()函数;例如,变量 c 可以表示为一个字符串: >>>str(c)"[1,2,'some text']" 工厂功能 有一系列函数可以直接创建变量类型。下面是最常用的。
However, you’ll get False as a result: Python >>> 2 == "2" False The integer 2 isn’t equal to the string "2". Therefore, you get False as a result. You can also use the != operator in the above expression, in which case you’ll get True as a result. Non-equality ...
You can use the built-in Python eval() to dynamically evaluate expressions from a string-based or compiled-code-based input. If you pass in a string to eval(), then the function parses it, compiles it to bytecode, and evaluates it as a Python expression. But if you call eval() wit...
Some Python users consider this "feature" to be more of a "bug". See implicit string concatenation for more on this feature. Boolean Python's two Boolean values are True and False. These values both have the type of bool, which stands for Boolean (named after George Boole, in case you...
print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False) Prints the values to a stream, or to sys.stdout by default. Optional keyword arguments: file: a file-like object (stream); defaults to the current sys.stdout. sep: string inserted between values, default a space...
print(value1,value2..., sep=' ', end='\n', file=sys.stdout, flush=False) Prints the values to a stream(流), or to sys.stdout(系统标准输出) by default(默认情况下) Optional keyword arguments: sep: string inserted between values(值之间插入的字符串), default a space. ...