python基礎-字串型別
阿新 • • 發佈:2020-12-01
# 1、作用 # 2、定義
# 定義:在單引號\雙引號\三引號內包含一串字元
name1 = 'jason' # 本質:name = str('任意形式內容')
name2 = "lili" # 本質:name = str("任意形式內容")
name3 = """ricky""" # 本質:name = str("""任意形式內容""")
# msg='hello' # msg=str('msg') # print(type(msg)) # 3、型別轉換 # str可以把任意其他型別都轉成字串 # res=str({'a':1}) # print(res,type(res))
>>> type(str([1,2,3])) # list->str
<class 'str'>
>>> type(str({"name":"jason","age":18})) # dict->str
<class 'str'>
>>> type(str((1,2,3))) # tuple->str
<class 'str'>
>>> type(str({1,2,3,4})) # set->str
<class 'str'>
# 4、使用:內建方法 # 4.1 優先掌握 # 4.1.1、按索引取值(正向取+反向取) :只能取 msg='hello world' # 正向取 # print(msg[0]) # print(msg[5]) # 反向取 # print(msg[-1]) # 只能取 # msg[0]='H' # 4.1.2、切片:索引的拓展應用,從一個大字串中拷貝出一個子字串 msg='hello world' # 顧頭不顧尾 # res=msg[0:5] #x # print(res) # print(msg) # 步長 # res=msg[0:5:2] # 0 2 4 # print(res) # hlo# 反向步長(瞭解) # res=msg[5:0:-1] # print(res) #" olle" msg='hello world' # res=msg[:] # res=msg[0:11] # print(res) # res=msg[::-1] # 把字串倒過來 # print(res) # 4.1.3、長度len # msg='hello world' # print(len(msg)) # 4.1.4、成員運算in和not in # 判斷一個子字串是否存在於一個大字串中 # print("alex" in "alex is sb") # print("alex" not in "alex is sb")# print(not "alex" in "alex is sb") # 不推薦使用 # 4.1.5、移除字串左右兩側的符號strip # 預設去掉的空格 # msg=' egon ' # res=msg.strip() # print(msg) # 不會改變原值 # print(res) # 是產生了新值 # 預設去掉的空格 # msg='****egon****' # print(msg.strip('*')) # 瞭解:strip只取兩邊,不去中間 # msg='****e*****gon****' # print(msg.strip('*')) # msg='**/*=-**egon**-=()**' # print(msg.strip('*/-=()')) # 應用 # inp_user=input('your name>>: ').strip() # inp_user=" egon" # inp_pwd=input('your password>>: ').strip() # if inp_user == 'egon' and inp_pwd == '123': # print('登入成功') # else: # print('賬號密碼錯誤') # 4.1.6、切分split:把一個字串按照某種分隔符進行切分,得到一個列表 # # 預設分隔符是空格 # info='egon 18 male' # res=info.split() # print(res) # # 指定分隔符 # info='egon:18:male' # res=info.split(':') # print(res) # 指定分隔次數(瞭解) # info='egon:18:male' # res=info.split(':',1) # print(res) # 4.1.7、迴圈 # info='egon:18:male' # for x in info: # print(x) # 4.2 需要掌握 #4.2.1、strip,lstrip,rstrip # msg='***egon****' # print(msg.strip('*')) # print(msg.lstrip('*')) # print(msg.rstrip('*')) #4.2.2、lower,upper # msg='AbbbCCCC' # print(msg.lower()) # print(msg.upper()) #4.2.3、startswith,endswith # print("alex is sb".startswith("alex")) # print("alex is sb".endswith('sb')) #4.2.4、format #4.2.5、split,rsplit:將字串切成列表 # info="egon:18:male" # print(info.split(':',1)) # ["egon","18:male"] # print(info.rsplit(':',1)) # ["egon:18","male"] #4.2.6、join: 把列表拼接成字串 # l=['egon', '18', 'male'] # res=l[0]+":"+l[1]+":"+l[2] # res=":".join(l) # 按照某個分隔符號,把元素全為字串的列表拼接成一個大字串 # print(res) # l=[1,"2",'aaa'] # ":".join(l) #4.2.7、replace # msg="you can you up no can no bb" # print(msg.replace("you","YOU",)) # print(msg.replace("you","YOU",1)) #4.2.8、isdigit # 判斷字串是否由純數字組成 # print('123'.isdigit()) # print('12.3'.isdigit()) # age=input('請輸入你的年齡:').strip() # if age.isdigit(): # age=int(age) # int("abbab") # if age > 18: # print('猜大了') # elif age < 18: # print('猜小了') # else: # print('才最了') # else: # print('必須輸入數字,傻子') # 4.3瞭解 #4.3.1、find,rfind,index,rindex,count msg='hello egon hahaha' # 找到返回起始索引 # print(msg.find('e')) # 返回要查詢的字串在大字串中的起始索引 # print(msg.find('egon')) # print(msg.index('e')) # print(msg.index('egon')) # 找不到 # print(msg.find('xxx')) # 返回-1,代表找不到 # print(msg.index('xxx')) # 丟擲異常 # msg='hello egon hahaha egon、 egon' # print(msg.count('egon')) #4.3.2、center,ljust,rjust,zfill # print('egon'.center(50,'*')) # print('egon'.ljust(50,'*')) # print('egon'.rjust(50,'*')) # print('egon'.zfill(10)) #4.3.3、expandtabs # msg='hello\tworld' # print(msg.expandtabs(2)) # 設定製表符代表的空格數為2 #4.3.4、captalize,swapcase,title # print("hello world egon".capitalize()) # print("Hello WorLd EGon".swapcase()) # print("hello world egon".title()) #4.3.5、is數字系列 #4.3.6、is其他 # print('abc'.islower()) # print('ABC'.isupper()) # print('Hello World'.istitle()) # print('123123aadsf'.isalnum()) # 字串由字母或數字組成結果為True # print('ad'.isalpha()) # 字串由由字母組成結果為True # print(' '.isspace()) # 字串由空格組成結果為True # print('print'.isidentifier()) # print('age_of_egon'.isidentifier()) # print('1age_of_egon'.isidentifier()) num1=b'4' #bytes num2=u'4' #unicode,python3中無需加u就是unicode num3='四' #中文數字 num4='Ⅳ' #羅馬數字 # isdigit只能識別:num1、num2 # print(num1.isdigit()) # True # print(num2.isdigit()) # True # print(num3.isdigit()) # False # print(num4.isdigit()) # False # isnumberic可以識別:num2、num3、num4 # print(num2.isnumeric()) # True # print(num3.isnumeric()) # True # print(num4.isnumeric()) # True # isdecimal只能識別:num2 print(num2.isdecimal()) # True print(num3.isdecimal()) # False print(num4.isdecimal()) # False
# 1.find,rfind,index,rindex,count # 1.1 find:從指定範圍內查詢子字串的起始索引,找得到則返回數字1,找不到則返回-1 >>> msg='tony say hello' >>> msg.find('o',1,3) # 在索引為1和2(顧頭不顧尾)的字元中查詢字元o的索引 1 # 1.2 index:同find,但在找不到時會報錯 >>> msg.index('e',2,4) # 報錯ValueError # 1.3 rfind與rindex:略 # 1.4 count:統計字串在大字串中出現的次數 >>> msg = "hello everyone" >>> msg.count('e') # 統計字串e出現的次數 4 >>> msg.count('e',1,6) # 字串e在索引1~5範圍內出現的次數 1 # 2.center,ljust,rjust,zfill >>> name='tony' >>> name.center(30,'-') # 總寬度為30,字串居中顯示,不夠用-填充 -------------tony------------- >>> name.ljust(30,'*') # 總寬度為30,字串左對齊顯示,不夠用*填充 tony************************** >>> name.rjust(30,'*') # 總寬度為30,字串右對齊顯示,不夠用*填充 **************************tony >>> name.zfill(50) # 總寬度為50,字串右對齊顯示,不夠用0填充 0000000000000000000000000000000000000000000000tony # 3.expandtabs >>> name = 'tony\thello' # \t表示製表符(tab鍵) >>> name tony hello >>> name.expandtabs(1) # 修改\t製表符代表的空格數 tony hello # 4.captalize,swapcase,title # 4.1 captalize:首字母大寫 >>> message = 'hello everyone nice to meet you!' >>> message.capitalize() Hello everyone nice to meet you! # 4.2 swapcase:大小寫翻轉 >>> message1 = 'Hi girl, I want make friends with you!' >>> message1.swapcase() hI GIRL, i WANT MAKE FRIENDS WITH YOU! #4.3 title:每個單詞的首字母大寫 >>> msg = 'dear my friend i miss you very much' >>> msg.title() Dear My Friend I Miss You Very Much # 5.is數字系列 #在python3中 num1 = b'4' #bytes num2 = u'4' #unicode,python3中無需加u就是unicode num3 = '四' #中文數字 num4 = 'Ⅳ' #羅馬數字 #isdigt:bytes,unicode >>> num1.isdigit() True >>> num2.isdigit() True >>> num3.isdigit() False >>> num4.isdigit() False #isdecimal:uncicode(bytes型別無isdecimal方法) >>> num2.isdecimal() True >>> num3.isdecimal() False >>> num4.isdecimal() False #isnumberic:unicode,中文數字,羅馬數字(bytes型別無isnumberic方法) >>> num2.isnumeric() True >>> num3.isnumeric() True >>> num4.isnumeric() True # 三者不能判斷浮點數 >>> num5 = '4.3' >>> num5.isdigit() False >>> num5.isdecimal() False >>> num5.isnumeric() False ''' 總結: 最常用的是isdigit,可以判斷bytes和unicode型別,這也是最常見的數字應用場景 如果要判斷中文數字或羅馬數字,則需要用到isnumeric。 ''' # 6.is其他 >>> name = 'tony123' >>> name.isalnum() #字串中既可以包含數字也可以包含字母 True >>> name.isalpha() #字串中只包含字母 False >>> name.isidentifier() True >>> name.islower() # 字串是否是純小寫 True >>> name.isupper() # 字串是否是純大寫 False >>> name.isspace() # 字串是否全是空格 False >>> name.istitle() # 字串中的單詞首字母是否都是大寫 False