python入门1

2023年5月31日 114次阅读
  1. 数据类型：整型，浮点型，复数型，布尔型，字符串，列表，元组，字典。列表，字典可变，字符串和元组不可变。
  2. 标识符：由数字，字母，下划线组成，数字不能开头，不能是python中的关键字。关键字有：
    False      class      finally    is         return None       continue   for        lambda     try True       def        from       non local   while and  del        global     not        with as         elif       if         or         yield assert     else       import     pass break      except     in         raise

     

  3. 查看python内建变量和函数：
dir(__builtins__)

显示结果是：[‘ArithmeticError’, ‘AssertionError’, ‘AttributeError’, ‘BaseException’, ‘BufferError’, ‘BytesWarning’, ‘DeprecationWarning’, ‘EOFError’, ‘Ellipsis’, ‘EnvironmentError’, ‘Exception’, ‘False’, ‘FloatingPointError’, ‘FutureWarning’, ‘GeneratorExit’, ‘IOError’, ‘ImportError’, ‘ImportWarning’, ‘IndentationError’, ‘IndexError’, ‘KeyError’, ‘KeyboardInterrupt’, ‘LookupError’, ‘MemoryError’, ‘NameError’, ‘None’, ‘NotImplemented’, ‘NotImplementedError’, ‘OSError’, ‘OverflowError’, ‘PendingDeprecationWarning’, ‘ReferenceError’, ‘RuntimeError’, ‘RuntimeWarning’, ‘StandardError’, ‘StopIteration’, ‘SyntaxError’, ‘SyntaxWarning’, ‘SystemError’, ‘SystemExit’, ‘TabError’, ‘True’, ‘TypeError’, ‘UnboundLocalError’, ‘UnicodeDecodeError’, ‘UnicodeEncodeError’, ‘UnicodeError’, ‘UnicodeTranslateError’, ‘UnicodeWarning’, ‘UserWarning’, ‘ValueError’, ‘Warning’, ‘ZeroDivisionError’, ‘_’, ‘__debug__’, ‘__doc__’, ‘__import__’, ‘__name__’, ‘__package__’, ‘abs’, ‘all’, ‘any’, ‘apply’, ‘basestring’, ‘bin’, ‘bool’, ‘buffer’, ‘bytearray’, ‘bytes’, ‘callable’, ‘chr’, ‘classmethod’, ‘cmp’, ‘coerce’, ‘compile’, ‘complex’, ‘copyright’, ‘credits’, ‘delattr’, ‘dict’, ‘dir’, ‘divmod’, ‘enumerate’, ‘eval’, ‘execfile’, ‘exit’, ‘file’, ‘filter’, ‘float’, ‘format’, ‘frozenset’, ‘getattr’, ‘globals’, ‘hasattr’, ‘hash’, ‘help’, ‘hex’, ‘id’, ‘input’, ‘int’, ‘intern’, ‘isinstance’, ‘issubclass’, ‘iter’, ‘len’, ‘license’, ‘list’, ‘locals’, ‘long’, ‘map’, ‘max’, ‘memoryview’, ‘min’, ‘next’, ‘object’, ‘oct’, ‘open’, ‘ord’, ‘pow’, ‘print’, ‘property’, ‘quit’, ‘range’, ‘raw_input’, ‘reduce’, ‘reload’, ‘repr’, ‘reversed’, ’round’, ‘set’, ‘setattr’, ‘slice’, ‘sorted’, ‘staticmethod’, ‘str’, ‘sum’, ‘super’, ‘tuple’, ‘type’, ‘unichr’, ‘unicode’, ‘vars’, ‘xrange’, ‘zip’]

abs这前是内建变量，之后是内建函数。

可能通过help来查看帮助信息：如看abs,abs求绝对值的，round函数进行四舍五入，round(4.5),得到结果是5.

help(abs)

       4.对于非内置函数，使用前要将函数所属的模块导入。如floor地板除，就是向下取整，和整数除 // 相同：

>>>floor(4.5)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'floor' is not defined
>>> import math
>>> math.floor(4.5)
4.0

以上为代码及显示结果。

模块：一个完整的python文件就是一个模块。

       文件：物理上的组织方式 math.py

       模块：逻辑上的组织方式 math

python 通常用 “ import 模块”的方式将现成模块中的函数，类等用到其它代码块中

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