1.概念
python中用',",''',"""引起來的內容稱爲字符串，可以保存少量數據並進行相應的操作
#先來看看str的源碼寫了什麼，方法:按ctrl+鼠標左鍵點str
class int(object): """ int(x=0) -> int or long int(x, base=10) -> int or long Convert a number or string to an integer, or return 0 if no arguments are given. If x is floating point, the conversion truncates towards zero. If x is outside the integer range, the function returns a long instead. If x is not a number or if base is given, then x must be a string or Unicode object representing an integer literal in the given base. The literal can be preceded by '+' or '-' and be surrounded by whitespace. The base defaults to 10. Valid bases are 0 and 2-36. Base 0 means to interpret the base from the string as an integer literal. >>> int('0b100', base=0) """ def bit_length(self): """ 返回表示該數字的時佔用的最少位數 """ """ int.bit_length() -> int Number of bits necessary to represent self in binary. >>> bin(37) '0b100101' >>> (37).bit_length() """ return 0 def conjugate(self, *args, **kwargs): # real signature unknown """ 返回該複數的共軛複數 """ """ Returns self, the complex conjugate of any int. """ pass def __abs__(self): """ 返回絕對值 """ """ x.__abs__() <==> abs(x) """ pass def __add__(self, y): """ x.__add__(y) <==> x+y """ pass def __and__(self, y): """ x.__and__(y) <==> x&y """ pass def __cmp__(self, y): """ 比較兩個數大小 """ """ x.__cmp__(y) <==> cmp(x,y) """ pass def __coerce__(self, y): """ 強制生成一個元組 """ """ x.__coerce__(y) <==> coerce(x, y) """ pass def __divmod__(self, y): """ 相除，得到商和餘數組成的元組 """ """ x.__divmod__(y) <==> divmod(x, y) """ pass def __div__(self, y): """ x.__div__(y) <==> x/y """ pass def __float__(self): """ 轉換爲浮點類型 """ """ x.__float__() <==> float(x) """ pass def __floordiv__(self, y): """ x.__floordiv__(y) <==> x//y """ pass def __format__(self, *args, **kwargs): # real signature unknown pass def __getattribute__(self, name): """ x.__getattribute__('name') <==> x.name """ pass def __getnewargs__(self, *args, **kwargs): # real signature unknown """ 內部調用 __new__方法或創建對象時傳入參數使用 """ pass def __hash__(self): """如果對象object爲哈希表類型，返回對象object的哈希值。哈希值爲整數。在字典查找中，哈希值用於快速比較字典的鍵。兩個數值如果相等，則哈希值也相等。""" """ x.__hash__() <==> hash(x) """ pass def __hex__(self): """ 返回當前數的 十六進制 表示 """ """ x.__hex__() <==> hex(x) """ pass def __index__(self): """ 用於切片，數字無意義 """ """ x[y:z] <==> x[y.__index__():z.__index__()] """ pass def __init__(self, x, base=10): # known special case of int.__init__ """ 構造方法，執行 x = 123 或 x = int(10) 時，自動調用，暫時忽略 """ """ int(x=0) -> int or long int(x, base=10) -> int or long Convert a number or string to an integer, or return 0 if no arguments are given. If x is floating point, the conversion truncates towards zero. If x is outside the integer range, the function returns a long instead. If x is not a number or if base is given, then x must be a string or Unicode object representing an integer literal in the given base. The literal can be preceded by '+' or '-' and be surrounded by whitespace. The base defaults to 10. Valid bases are 0 and 2-36. Base 0 means to interpret the base from the string as an integer literal. >>> int('0b100', base=0) # (copied from class doc) """ pass def __int__(self): """ 轉換爲整數 """ """ x.__int__() <==> int(x) """ pass def __invert__(self): """ x.__invert__() <==> ~x """ pass def __long__(self): """ 轉換爲長整數 """ """ x.__long__() <==> long(x) """ pass def __lshift__(self, y): """ x.__lshift__(y) <==> x<<y """ pass def __mod__(self, y): """ x.__mod__(y) <==> x%y """ pass def __mul__(self, y): """ x.__mul__(y) <==> x*y """ pass def __neg__(self): """ x.__neg__() <==> -x """ pass @staticmethod # known case of __new__ def __new__(S, *more): """ T.__new__(S, ...) -> a new object with type S, a subtype of T """ pass def __nonzero__(self): """ x.__nonzero__() <==> x != 0 """ pass def __oct__(self): """ 返回改值的 八進制 表示 """ """ x.__oct__() <==> oct(x) """ pass def __or__(self, y): """ x.__or__(y) <==> x|y """ pass def __pos__(self): """ x.__pos__() <==> +x """ pass def __pow__(self, y, z=None): """ 冪，次方 """ """ x.__pow__(y[, z]) <==> pow(x, y[, z]) """ pass def __radd__(self, y): """ x.__radd__(y) <==> y+x """ pass def __rand__(self, y): """ x.__rand__(y) <==> y&x """ pass def __rdivmod__(self, y): """ x.__rdivmod__(y) <==> divmod(y, x) """ pass def __rdiv__(self, y): """ x.__rdiv__(y) <==> y/x """ pass def __repr__(self): """轉化爲解釋器可讀取的形式 """ """ x.__repr__() <==> repr(x) """ pass def __str__(self): """轉換爲人閱讀的形式，如果沒有適於人閱讀的解釋形式的話，則返回解釋器課閱讀的形式""" """ x.__str__() <==> str(x) """ pass def __rfloordiv__(self, y): """ x.__rfloordiv__(y) <==> y//x """ pass def __rlshift__(self, y): """ x.__rlshift__(y) <==> y<<x """ pass def __rmod__(self, y): """ x.__rmod__(y) <==> y%x """ pass def __rmul__(self, y): """ x.__rmul__(y) <==> y*x """ pass def __ror__(self, y): """ x.__ror__(y) <==> y|x """ pass def __rpow__(self, x, z=None): """ y.__rpow__(x[, z]) <==> pow(x, y[, z]) """ pass def __rrshift__(self, y): """ x.__rrshift__(y) <==> y>>x """ pass def __rshift__(self, y): """ x.__rshift__(y) <==> x>>y """ pass def __rsub__(self, y): """ x.__rsub__(y) <==> y-x """ pass def __rtruediv__(self, y): """ x.__rtruediv__(y) <==> y/x """ pass def __rxor__(self, y): """ x.__rxor__(y) <==> y^x """ pass def __sub__(self, y): """ x.__sub__(y) <==> x-y """ pass def __truediv__(self, y): """ x.__truediv__(y) <==> x/y """ pass def __trunc__(self, *args, **kwargs): """ 返回數值被截取爲整形的值，在整形中無意義 """ pass def __xor__(self, y): """ x.__xor__(y) <==> x^y """ pass denominator = property(lambda self: object(), lambda self, v: None, lambda self: None) # default """ 分母 = 1 """ """the denominator of a rational number in lowest terms""" imag = property(lambda self: object(), lambda self, v: None, lambda self: None) # default """ 虛數，無意義 """ """the imaginary part of a complex number""" numerator = property(lambda self: object(), lambda self, v: None, lambda self: None) # default """ 分子 = 數字大小 """ """the numerator of a rational number in lowest terms""" real = property(lambda self: object(), lambda self, v: None, lambda self: None) # default """ 實屬，無意義 """ """the real part of a complex number""" int
2.字符串的索引和切片
#索引
#索引就是下標，切記，下標從0開始 s = "大河向東流去" print(s[0]) #大 #從0開始取 print(s[1]) #河 print(s[2]) #向 print(s[3]) #東 print(s[4]) #流 print(s[5]) #去 print(s[6]) #索引不能超過邊界，要不然會報錯 print(s[-1]) #-1就是倒着從後面取 print(s[-2]) print(s[-3]) print(s[-4]) print(s[-5]) print(s[-6])
#切片
#切片[起始位置：結束位置] #特點：1、顧頭不顧尾 2、只能從左往右切 #例子： s = "改革春風吹滿面"
print(s[1:3]) #從1切到3，但是取不到3
#革春 #因爲是下標從0開始，所以1就是革
print(s[1:]) #從1開始切，切到結尾 #革春風吹滿面
print(s[:2]) #從頭開始切到2
#改革
print(s[:]) #從頭到尾
#改革春風吹滿面
print(s[-1:-3]) #這樣從右往左切會是空值 print(s[-3:-1]) #只能從左往右切
#吹滿
#跳着取值，步長
#步長：如果是整數，就從左往右取，如果是負數就從右往左取 print(s[-1:-3:-1]) # - 表示反方向，從右往左 print(s[3:9:2]) #表示3到9中間每隔2位取一個 print(s[4:10:3]) #表示4到10中間每隔3取一位 print(s[-3:-9:-2]) #從右往左每個2位取一個
3.字符串相關操作
#注意點：
#注意：字符串是不可變的對象，所有任何操作對源字符串是不會有任何影響的 #例如 s = "I am a teacher" s.capitalize() print(s) #I am a teacher
#1.大小寫的相互轉換
#關鍵字 # capitalize():將首字母變成大寫 # lower():全部替換成小寫 # upper():全部替換成大寫 # swapcase():大小寫互換 # casefold():轉換成小寫 # titile():每個被特殊字符隔開的首字母大寫
#例子：
s = "This is teacher and Student" s1 = s.capitalize() #將首字母變成大寫 print(s1) #This is teacher and student s2 = s.lower() #全部轉換成小寫 print(s2) #this is teacher and student s3 = s.upper() #全部轉換成大寫 print(s3) #THIS IS TEACHER AND STUDENT s4 = s.swapcase() #大小寫互相轉換 print(s4) #tHIS IS TEACHER AND sTUDENT s5 = s.casefold() #轉換成小寫，這個能識別出所有字母，但lower有些不支持 print(s5) #this is teacher and student
#2.切來切去
#關鍵字 # center():內容居中 # strip():去掉左右兩端的空格 # lstrip():去掉左邊的空格 # rstrip():去掉右邊的空格 # replace（old,new）：字符替換 # split（）：切割
#例子：
#1.拉長的長度:center() s = "nb" s1 = s.center(10,"#") #強行使用#號在原字符串左右兩端進行拼接，拼接成10個單位 print(s1) # 更改tab的長度 s6 = "alex wusir\teggon" print(s6) print(s6.expandtabs()) # 可以改變\t的⻓長度, 默認⻓長度更更改爲8 #2.去空格 s = " guoke boy is " s1 = s.strip() #默認去掉兩邊的空格 print(s1) #打印出來的時候就會發現兩邊沒有空格 s2 = s.lstrip() #去掉左邊的空格 print(s2) s3 = s.rstrip() #去掉右邊的空格 print(s3) #strip()應用 # 設置用戶交互式登陸的時候，如果不加strip()，當用戶如輸入用戶名後面加了空格，那麼就會報錯 # 如果加了strip(),就可以去掉兩邊的空格 username = input("請輸入用戶名:").strip() password = input("請輸入密碼:").strip() if username == 'cw' and password == '123': print("登陸成功") else: print("登陸失敗") #指定去掉的元素 s = "nb boy guoke nb nb tiantian sb" print(s.strip("nb")) #3.字符串替換:replace() s = "student，戰狼，teacher,小豬佩奇_eat，少年的你" s1 = s.replace("少年的你","中國機長") #將少年的你替換成中國機長 s2 = s.replace("小豬","貓貓") #將小豬替換成貓貓 print(s1,s2) s3 = s.replace('e','nb',2) #將e替換成nb，替換前兩個 print(s3) #4.字符串切割：split() s4 = "fd,fwe,tet,rer,aggo" lst = s4.split(",") #字符串切割，根據,進行切割 print(lst) s5 = s4.split("e") #使用什麼進行切割就會損失掉什麼 print(s5) #坑點 # s7 = "湖邊哈哈美麗美麗湖人湖邊" # lst = s7.split("湖邊") #如果切割符在左右兩端，那麼一定會出現空字符串 # print(lst) # print(bool(lst)) #可以看到返回是True,因爲是空字符串
#3.查找相關
#關鍵字: # startswith():判斷是否以xxx開頭 # endswith():判斷是否以xxx結尾 # count():查看那個字符出現的次數 # find():查看關鍵字在什麼位置，沒有找到的話就返回-1 # index():求索引的位置：如果沒找到字符串就會報錯
#例子：
s = "我是一個boy，我喜歡python，java等編程語言" s1 = s.startswith("我是一個") #判斷是否以我開頭，如果是就會返回True，否則返回False print(s1) #True s2 = s.startswith("boy") #可以看出返回的結果是False print(s2) #False s3 = s.endswith("語言") #判斷是否以"語言"位結尾，是就會返回True，否則返回False print(s3) #True s4 = s.endswith("我們") #可以看出不是以我們結尾就返回False print(s4) #False s5 = s.count("a") #統計"a"出現的次數 print(s5) #2 s6 = s.find("java") #查看Java出現的位置,只找第一次出現的位置，沒有就返回-1 print(s6) #18 s7 = s.find("a",20,29) #切片找，指定位置找a，從20-29中間找有沒有a print(s7) #21 s8 = s.index("java") #查找java的位置 print(s8) #18 # s9 = s.index("z") #index如果沒有查找到的話就會報錯，寫程序的就不用使用index，否則整個程序都會崩掉了，使用find # print(s9)
#4.條件判斷相關
#關鍵字 # isalnum():判斷是否由字母和數字組成 # isalpha():判斷是否由字母組成 # isdigit():判斷是否由數字組成 # isdecimal():判斷是否由數字組成 # isnumeric():判斷是否由數字組成 #中文也識別
#例子：
s1 = "12345" s2 = "123abc" s3 = "abcde" s4 = "_abdf@" s5 = "壹仟叄佰肆拾" print(s1.isdigit()) #判斷是否由數字組成，如果是就返回True，否則Fase #True print(s2.isalnum()) #判斷是否由數字和字母組成 #True print(s3.isalpha()) #判斷是否由字母組成 #True print(s5.isnumeric()) #判斷是否由數字組成，可以是大寫的，如果是字符串就報錯 #True print(s1.isdecimal()) #判斷是否由數字組成 #True #練習，用算法判斷某一個字符串是否是小數 s17 = "-123.12" s17 = s17.replace("-", "") # 替換掉負號 if s17.isdigit(): print("是整數") else: if s17.count(".") == 1 and not s17.startswith(".") and not s17.endswith("."): print("是⼩小數") else: print("不不是⼩小數") #過程理解：首先將符號替換成空字符串，然後進入判斷變量是否是數字組成 #很顯然是沒有由數字組成，所有就走else,又進入如果判斷，如果統計點符號等於1 #和不是以點開頭和不是以點結尾，滿足條件，所以打印是小小數
#5.計算字符串的長度
#關鍵字 #len():計算機字符串的長度
#例子：
s1 = "我是你的小呀小蘋果" ret = len(s1) print(ret) #9 #注意：len()是python的內置函數，所以訪問方式也不一樣，記住len()和print()方式一樣
#6.join
#join:將列表轉換成字符串 #注意:join(裏面放的是可迭代對象)
#例子
lst = ["蔣小雨","張衝","魯炎"] s = "_".join(lst) print(s) #蔣小雨_張衝_魯炎 s = "_".join("武黑臉") print(s) #武_黑_臉 #將字符串轉換成列表：split() s = "馬雲,移動,雷子" lst = s.split(",") print(lst) #['馬雲', '移動', '雷子']