Python 3 7 字串 str 學習

定義字串

string =

''string1 =
'this is a string' 
string2 = r'this is a raw string'
# 原始字串, 轉義字元等均不轉義原樣輸出

length =

len(string1)
print
(length)
# 16

if

'is'
in string1:
print
('string1 含有 `is`'
)if string1 == string2:
print
('string1 與 string2 一樣'
)

n_str =

'this is '
+'a string'
# 使用 `+` 拼接
print
(n_str)
# this is a string
n_str =
'this is '
n_str +=
'a string'
# 使用 `+=` 拼接
print
(n_str)
# this is a string
n_str2 =
'num: '
+str(4
)# 拼接數字
print
(n_str2)
# num: 4

format_str =

'%s is a string. length: %d'%(
'this',16
)# 格式化, %f、%d、%s等格式, 和 c 語言基本上一致
print
(format_str)
# this is a string. length: 16
format_str =
'th{} a '
.format
('is'
, p2=
'string'
, p1=
'is'
)# format_str = 'th a '.format(p2='string', p1='is')
# format_str = 'th a '.format('string', 'is')
# format_str = ' is a '.format('this', 'string')
# format_str = '{} is a {}'.format('this', 'string')
print
(format_str)
# this is a string

t_str =

'the number is '
.format
(num=88)
print
(t_str)
# the number is 88
t_str =
'the number is '
.format
(num=88)
# 浮點型
print
(t_str)
# the number is 88.000000
t_str =
'the number is '
.format
(num=88)
# 浮點型-保留2位小數
print
(t_str)
# the number is 88.00
t_str =
'the number is '
.format
(num=88)
# 浮點型-保留2位小數，指定寬度, 如果不足則在前面補0
print
(t_str)
# the number is 0000088.00
t_str =
'the number is '
.format
(num=88)
# 二進位制
print
(t_str)
# the number is 1011000

python 分正索引與負索引, 正索引和其他程式語言一樣；負索引是從最後往前標識, 負索引是從-1開始的

切片格式：str[擷取開始索引:擷取結束索引]

t_str = string1[:-

3]# 從索引0開始擷取到倒數第三個字元之前的位置
# t_str = string1[0:-3]
print
(t_str)
# this is a str
t_str = string1[:3
]# 從索引0開始擷取到索引3字元之前的位置
# t_str = string1[0:3]
print
(t_str)
# thi
t_str = string1[5:
7]# 從索引5開始擷取到索引7之前的位置
print
(t_str)
# is

array = string1.split(

' ')
# 以空格分割字串
print
(array)
# ['this', 'is', 'a', 'string']
t_str =
'-'.join(array)
# 以 `-` 將字串陣列拼接成字串
print
(t_str)
# this-is-a-string

upp = string1.upper(

)# 轉為大寫
print
(upp)
# this is a string
low = upp.lower(
)# 轉為小寫
print
(low)
# this is a string

t_str =

' \n\n this is a string \n'
.strip(
)print
(t_str)
# this is a string

index = string1.find(

'is a'
)# 如果查詢到子字串則返回子串的第乙個字元的索引，否則返回 `-1`
print
(index)
# 5

t_str = string1.replace(

'string'
,'raw string'
)print
(t_str)
# this is a raw string

for char in string1:

print
(char)
'''thi
s is
a strin
g'''

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