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摘要：數(shù)值類型整形長整形有長整形沒有長整形浮點型復(fù)數(shù)類型查看幫助可以使用什么方法，實現(xiàn)什么功能共軛虛部實部初學(xué)階段，避免使用開頭的內(nèi)置功能字符串?dāng)?shù)據(jù)類型學(xué)生管理系統(tǒng)學(xué)生管理系統(tǒng)數(shù)據(jù)類型的轉(zhuǎn)換在中，所有的數(shù)據(jù)類型都可以作為內(nèi)置函數(shù)，用來轉(zhuǎn)換數(shù)
數(shù)值類型 1.整形
Python 2.7.5 (default, Feb 11 2014, 07:46:25) >>> aint=3 >>> type(aint)2.長整形Python 3.6.4 (default, Aug 6 2018, 22:54:20) >>> aint=3 >>> type(aint)
python2#有長整形 >>> along=1728219876932764873264934692 >>> type(along)3.浮點型python3#沒有長整形 >>> along=1728219876932764873264934692 >>> type(along)
1.344,12000000=12e6=1.2e7=0.12e7,0.012=1.2e-2
python2 >>> afloat=12e3 >>> afloat 12000.0 >>> type(afloat)4.復(fù)數(shù)類型python3 >>> afloat=12e3 >>> type(afloat)
查看幫助：可以使用什么方法，實現(xiàn)什么功能？acomplex=3j+8
type(acomplex)
help(acomplex)dir(acomplex)
["__abs__", "__add__", "__class__", "__coerce__", "__delattr__", "__div__", "__divmod__", "__doc__", "__eq__", "__float__", "__floordiv__", "__format__", "__ge__", "__getattribute__", "__getnewargs__", "__gt__", "__hash__", "__init__", "__int__", "__le__", "__long__", "__lt__", "__mod__", "__mul__", "__ne__", "__neg__", "__new__", "__nonzero__", "__pos__", "__pow__", "__radd__", "__rdiv__", "__rdivmod__", "__reduce__", "__reduce_ex__", "__repr__", "__rfloordiv__", "__rmod__", "__rmul__", "__rpow__", "__rsub__", "__rtruediv__", "__setattr__", "__sizeof__", "__str__", "__sub__", "__subclasshook__", "__truediv__", "conjugate", "imag", "real"]
>>> acomplex.conjugate() #共軛 (8-3j) >>> acomplex.imag #虛部 3.0 >>> acomplex.real #實部 8.0
初學(xué)階段，避免使用"__"開頭的內(nèi)置功能
>>> astring="hello" >>> type(astring)數(shù)據(jù)類型的轉(zhuǎn)換>>> dir(astring) ["__add__", "__class__", "__contains__", "__delattr__", "__doc__", "__eq__", "__format__", "__ge__", "__getattribute__", "__getitem__", "__getnewargs__", "__getslice__", "__gt__", "__hash__", "__init__", "__le__", "__len__", "__lt__", "__mod__", "__mul__", "__ne__", "__new__", "__reduce__", "__reduce_ex__", "__repr__", "__rmod__", "__rmul__", "__setattr__", "__sizeof__", "__str__", "__subclasshook__", "_formatter_field_name_split", "_formatter_parser", "capitalize", "center", "count", "decode", "encode", "endswith", "expandtabs", "find", "format", "index", "isalnum", "isalpha", "isdigit", "islower", "isspace", "istitle", "isupper", "join", "ljust", "lower", "lstrip", "partition", "replace", "rfind", "rindex", "rjust", "rpartition", "rsplit", "rstrip", "split", "splitlines", "startswith", "strip", "swapcase", "title", "translate", "upper", "zfill"] >>> help(astring.center) >>> astring.center(40,"*") "*****************hello******************" >>> print("學(xué)生管理系統(tǒng)".center(40,"*")) ***********學(xué)生管理系統(tǒng)***********
-在python中，所有的數(shù)據(jù)類型都可以作為內(nèi)置函數(shù)，用來轉(zhuǎn)換數(shù)據(jù)類型：
>>> int(3.10) 3 >>> str(3) "3" >>> type(str(3))如何刪除內(nèi)存中的變量>>> float(3) 3.0 >>> complex(2) (2+0j)
>>> afloat=2e12 >>> del afloat >>> afloat Traceback (most recent call last): File "布爾數(shù)據(jù)類型", line 1, in NameError: name "afloat" is not defined
bool:只有兩個值(True,Flase)
>>>a = 1 >>> bool(a) True >>> bool(0) False >>> name = "we" >>> bool(a) True運算符 1.算術(shù)運算符
+,-,,*,/,%,//
2.賦值運算符=,+=,-=,/=,%=,*=
3.關(guān)系運算符,>=,<,<=,!=,==4.邏輯運算符
邏輯與and
邏輯或or
邏輯非not
python2
>>> 5/2 2 >>> 100/300 0 >>> 5/2.0 2.5 >>> 100/300.0 0.3333333333333333 >>> from __future__ import division >>> 5/3 1.6666666666666667
python3
vim empty.py
#判斷輸入為空時，輸出"Error"
value=input("請輸入：")
if not value:
print("Erros")
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