Python String函數_ZenDei技術網路在線

1.str.capitalize() 將原字元串內的首字母轉成大寫,其他部分小寫,再返回新字元串 Output： 2.str.upper() 將原字元串的字母轉為大寫 Output: 3.str.lower() 將原字元串的字母轉為小寫 Output: 4.str.swapcase() 將原字元串內 ...

s = "abcaDa a"
s2 = "123a abc ABCSAa s "
s3 = "\tas \t\tb123"
s4 = '    &abc123 c ##    '

1.str.capitalize()

將原字元串內的首字母轉成大寫,其他部分小寫,再返回新字元串

print("s.capitalize() = {function}".format(function = s.capitalize()))

Output：

s.capitalize() = Abcada a

2.str.upper()

將原字元串的字母轉為大寫

print("s.upper() = {function}".format(function = s.upper()))

Output:

s.upper() = ABCADA A

3.str.lower()

將原字元串的字母轉為小寫

print("s.lower() = {function}".format(function = s.lower()))

Output:

s.lower() = abcada a

4.str.swapcase()

將原字元串內的大寫小寫反轉

print("s.swapcase() = {function}".format(function = s.swapcase()))

Output:

s.swapcase() = ABCAdA A

5.str.title()

原字元串內如果有特殊字元(包括數字)連接字母,則將特殊字元後的首個英文字母轉化為大寫形態,並返回新字元串

print("s2.title() = {function}".format(function = s2.title()))

Output:

s2.title() = 123A Abc Abcsaa S

6.str.center()

str.center(寬度,填充字元) 將字元串以居中的格式返回,若寬度值比len(s)小則返回原字元串,填充以從左到右為規則,填充字元的預設值為空格,值可以自己更改

print("s2.center() = {function}".format(function = s2.center(19,'&')))
print("s2.center() = {function}".format(function = s2.center(20,'&')))

Output:

#s2 = 123a abc ABCSAa s
s2.center() = &123a abc ABCSAa s 
s2.center() = &123a abc ABCSAa s &

7.str.expandtabs()

str.expandtabs(tabsize = 8) 將原字元串中\t以前的字元補滿8位(預設),tabsize的值從0-7即8位,在0-7中任意取值則預設tabsize = 8,此後

往上+1，就相當於增加一個空格

print("s3.expandtabs ={function}".format(function = s3.expandtabs()))
print("s3.expandtabs ={function}".format(function = s3.expandtabs(0)))
print("s3.expandtabs ={function}".format(function = s3.expandtabs(5)))
print("s3.expandtabs ={function}".format(function = s3.expandtabs(8)))
print("s3.expandtabs ={function}".format(function = s3.expandtabs(9)))

Output:

#s3 = "\tas \t\tb123"
s3.expandtabs =        as              b123
s3.expandtabs =as b123
s3.expandtabs =     as        b123
s3.expandtabs =        as              b123
s3.expandtabs =         as                b123

8.String_len = len(str)

公共方法,計算字元串的長度

print("s2_length = {0}".format(len(s2)))

Output:

s2_length = 18

9.str.startswith()

str.startswith(substr,strbeg,strend) 判斷原字元串是否以子字元串開頭可以用切片的形式進行判斷(以顧頭不顧尾為原則),這裡的strend要比strbeg大否則傳回false 函數結果返回一個布爾值

print("s.startswith() = {function}".format(function = s.startswith('ab')))
print("s.startswith() = {function}".format(function = s.startswith('D',2)))
print("s.startswith() = {function}".format(function = s.startswith('c',2,5)))
print("s.startswith() = {function}".format(function = s.startswith('c',2,100)))

Output:

#s = abcaDa a
s.startswith() = True
s.startswith() = False
s.startswith() = True
s.startswith() = True

10.str.endswith()

str.endswith(substr,strbeg,strend) 判斷字元串是否以子字元串結尾結果返回布爾值,這裡的strend要比strbeg小否則傳回false 和startswith()一樣要從左到右為原則

print("s.endswith() = {function}".format(function = s.endswith('Da a')))
print("s.endswith() = {function}".format(function = s.endswith('a',-1)))
print("s.endswith() = {function}".format(function = s.endswith('Da a',-4)))
print("s.endswith() = {function}".format(function = s.endswith('c',-8,-5)))
print("s.endswith() = {function}".format(function = s.endswith('c',-7,-5)))
print("s.endswith() = {function}".format(function = s.endswith('c',-7,-4)))
print("s.endswith() = {function}".format(function = s.endswith('Da a',-1,6)))

Output:

#s = abcaDa a
s.endswith() = True
s.endswith() = True
s.endswith() = True
s.endswith() = True
s.endswith() = True
s.endswith() = False
s.endswith() = False

11.str.find()

str.find(substr,strbeg,strend) 尋找字元串中是否存在該子字元串並返回其索引,找不到則返回-1 若同時出現相同的字元串則返回最先找到

的子字元串索引,切片(遵循顧頭不顧尾原則)

print("s.find() = {function}".format(function = s.find('a')))
print("s.find() = {function}".format(function = s.find('ab')))
print("s.find() = {function}".format(function = s.find('f')))
print("s.find() = {function}".format(function = s.find('b',-8,-5)))
print("s.find() = {function}".format(function = s.find('b',0)))

Output:

s.find() = 0
s.find() = 0
s.find() = -1
s.find() = 1
s.find() = 1

12.str.index()

str.index(substr,strbeg,strend) 與find()的功能大致相同，但子字元串不存在於字元串中就會報錯,結果返回索引

print("s.index() = {function}".format(function = s.index('a')))
print("s.index() = {function}".format(function = s.index('ab')))
print("s.index() = {function}".format(function = s.index('D',-8,5)))
print("s.index() = {function}".format(function = s.index('b',0)))

Output:

#s = abcaDa a
s.index() = 0
s.index() = 0
s.index() = 4
s.index() = 1

13.str.strip()

str.strip([chars]) 去掉字元串中首和尾的字元預設刪除的是空格 chars可以自行更改

print("s3.strip() = {function}".format(function = s3.strip()))

Output:

#s3 =    as              b123
s3.strip() = as                 b123

14.str.rstrip()

str.rstrip([chars]) 去掉字元串右邊的字元預設刪除的是空格返回值為刪除後的新字元串

print("s4.rstrip() = {function}".format(function = s4.rstrip()))
print("s4.rstrip() = {function}".format(function = s4.rstrip('# c')))

Output:

#s4 = '    &abc123 c ##    '
s4.rstrip() =     &abc123 c ##
s4.rstrip() =     &abc123

15.str.lstrip()

str.lstrip([chars]) 去掉字元串左邊的字元預設刪除的是空格返回值為刪除後的新字元串

print("s4.lstrip() = {function}".format(function = s4.lstrip()))
print("s4.lstrip() = {function}".format(function = s4.lstrip(' &')))

Output:

#s4 = '    &abc123 c ##    '
s4.lstrip() = &abc123 c ##    
s4.lstrip() = abc123 c ##

16.str.count()

str.count(substr,start,end) start為第一個字元，這裡預設為0 end未結束搜索的位置,預設為len(s) 主要功能統計字元串中某個字元出現

的個數並返回個數

print("s.count() = {function}".format(function = s.count('a')))
print("s.count() = {function}".format(function = s.count('Fa')))
print("s.count() = {function}".format(function = s.count('a',-7)))

Output:

#s = "abcaDa a"
s.count() = 4
s.count() = 0
s.count() = 3

17.str.split()

str.split(substr = " ",num = s.count(str)) 主要作用分割字元串這裡的substr預設以空格分割,num為總共切割的次數,若num有數值怎分割num+1個字元串分割後將字元串轉化為list形式 substr會在分割後消失

print("s2.split() = {function}".format(function = s2.split()))
print("s2.split() = {function}".format(function = s2.split(' ',0)))
print("s2.split() = {function}".format(function = s2.split('a',1)))
print("s2.split() = {function}".format(function = s2.split('a',-1)))

Output:

#s2 = "123a abc ABCSAa s "
s2.split() = ['123a', 'abc', 'ABCSAa', 's']
s2.split() = ['123a abc ABCSAa s ']
s2.split() = ['123', ' abc ABCSAa s ']
s2.split() = ['123', ' ', 'bc ABCSA', ' s ']

18.str.format()

三種用法：

print("s = {}|s2 = {}|s3 = {}".format(s,s2,s3))
print("s = {0}|s2 = {1}|s3 = {2}|s = {0}|s3 = {2}".format(s,s2,s3))
print("s = {s}{sep}s2 = {s2}{sep}s3 = {s3}".format(s = s,s2 = s2,s3 = s3,sep = '|'))

Output:

s = abcaDa a|s2 = 123a abc ABCSAa s |s3 =       as              b123
s = abcaDa a|s2 = 123a abc ABCSAa s |s3 =       as              b123|s = abcaDa a|s3 =  as              b123
s = abcaDa a|s2 = 123a abc ABCSAa s |s3 =       as              b123

當占位符不按順序寫會報錯 tuple index out of range

19.str.replace()

s.replace(old,new,max) old為將被替換的字元串,new為替換old的字元串,max為替換次數將字元串進行替換,若old未存在原字元串內則返回原

字元串

print("s.replace() = {function}".format(function = s.replace('ac','A')))
print("s.replace() = {function}".format(function = s.replace('a','A')))
print("s.replace() = {function}".format(function = s.replace('a','A',2)))

Output:

#s = "abcaDa a"
s.replace() = abcaDa a
s.replace() = AbcADA A
s.replace() = AbcADa a

20.is函數

　　str.isalnum()　　#判斷是否由數字或字母組成

　　str.isalpha()　　 #判斷是否含有字母

　　str.isdecimal()　　#判斷是否含有十進位數字

　　str.isdigit()　　#判斷是否含有數字

　　str.islower()　　#判斷是否含有小寫字母

　　str.isupper()　　#判斷是否含有大寫字母

　　str.isnumeric()　　#判斷是否只包含數字字元

　　str.isspace()　　#判斷是否只含有空格

　　str.istitle()　　#判斷是否經過title()函數處理過後的標題

21.join()

str.join(sequence)　　sequence為要連接的元素序列,函數作用是將指定字元串與原字元串中每一個字元一一連接

s = 'alex'
print('&&'.join(s)) #a&&l&&e&&x
l = ['a','l','e','x']
print('+'.join(l))  #a+l+e+x
t = ('a','b')
print('*'.join(t))  #a*b

PS:String索引對應