Rentetan ialah objek yang mengandungi urutan aksara. Aksara ialah rentetan panjang 1. Dalam Python, aksara individu juga merupakan rentetan. Tetapi yang lebih menarik ialah tiada jenis data aksara dalam bahasa pengaturcaraan Python, tetapi terdapat jenis data aksara dalam bahasa pengaturcaraan lain seperti C, Kotlin dan Java
Kita boleh menggunakan petikan tunggal, berganda. petikan, petikan Tiga atau fungsi str() untuk mengisytiharkan rentetan Python. Coretan kod berikut menunjukkan cara mengisytiharkan rentetan dalam Python:
# A single quote string single_quote = 'a'# This is an example of a character in other programming languages. It is a string in Python # Another single quote string another_single_quote = 'Programming teaches you patience.' # A double quote string double_quote = "aa" # Another double-quote string another_double_quote = "It is impossible until it is done!" # A triple quote string triple_quote = '''aaa''' # Also a triple quote string another_triple_quote = """Welcome to the Python programming language. Ready, 1, 2, 3, Go!""" # Using the str() function string_function = str(123.45)# str() converts float data type to string data type # Another str() function another_string_function = str(True)# str() converts a boolean data type to string data type # An empty string empty_string = '' # Also an empty string second_empty_string = "" # We are not done yet third_empty_string = """"""# This is also an empty string: ''''''
Cara lain untuk mendapatkan rentetan dalam Python ialah menggunakan fungsi input(). Fungsi input() membolehkan kami memasukkan nilai yang dimasukkan ke dalam program menggunakan papan kekunci. Nilai yang disisipkan dibaca sebagai rentetan, tetapi kita boleh menukarnya kepada jenis data lain:
# Inputs into a Python program input_float = input()# Type in: 3.142 input_boolean = input() # Type in: True # Convert inputs into other data types convert_float = float(input_float)# converts the string data type to a float convert_boolean = bool(input_boolean) # converts the string data type to a bool
Kami menggunakan fungsi type() untuk menentukan jenis data objek dalam Python, yang mengembalikan kelas daripada objek itu. Apabila objek adalah rentetan, ia mengembalikan kelas str. Begitu juga, apabila objek ialah kamus, integer, float, tuple atau boolean, ia mengembalikan kelas dict, int, float, tuple, bool. Sekarang mari kita gunakan fungsi type() untuk menentukan jenis data pembolehubah yang diisytiharkan dalam coretan kod sebelumnya:
# Data types/ classes with type() print(type(single_quote)) print(type(another_triple_quote)) print(type(empty_string)) print(type(input_float)) print(type(input_boolean)) print(type(convert_float)) print(type(convert_boolean))
ord() menukar aksara Python dengan panjang 1 (. satu aksara) Rentetan ditukar kepada perwakilan perpuluhan pada jadual ASCII, dan fungsi chr() menukarkan perwakilan perpuluhan kembali kepada rentetan. Contohnya:
Output:import string # Convert uppercase characters to their ASCII decimal numbers ascii_upper_case = string.ascii_uppercase# Output: ABCDEFGHIJKLMNOPQRSTUVWXYZ for one_letter in ascii_upper_case[:5]:# Loop through ABCDE print(ord(one_letter))
65 66 67 68 69
# Convert digit characters to their ASCII decimal numbers ascii_digits = string.digits# Output: 0123456789 for one_digit in ascii_digits[:5]:# Loop through 01234 print(ord(one_digit))
48 49 50 51 52
decimal_rep_ascii = [37, 44, 63, 82, 100] for one_decimal in decimal_rep_ascii: print(chr(one_decimal))
% , ? R d
Harta Rentetan
immutable_string = "Accountability"
print(len(immutable_string))
print(immutable_string.index('A'))
print(immutable_string.index('y'))
14 0 13
immutable_string = "Accountability" # Assign a new element at index 0 immutable_string[0] = 'B'
--------------------------------------------------------------------------- TypeError Traceback (most recent call last) ~AppDataLocalTemp/ipykernel_11336/2351953155.py in 2 3 # Assign a new element at index 0 ----> 4 immutable_string[0] = 'B' TypeError: 'str' object does not support item assignment
immutable_string = "Accountability" print(id(immutable_string)) immutable_string = "Bccountability" print(id(immutable_string) test_immutable = immutable_string print(id(test_immutable))
2693751670576 2693751671024 2693751671024
Concatenation: Gabungkan dua atau lebih rentetan bersama-sama untuk mendapatkan rentetan baharu dengan tanda +. Contohnya:
Output:first_string = "Zhou" second_string = "luobo" third_string = "Learn Python" fourth_string = first_string + second_string print(fourth_string) fifth_string = fourth_string + " " + third_string print(fifth_string)
Zhouluobo Zhouluobo Learn Python
print("Ha" * 3)
HaHaHa
main_string = "I learned English and Python with ZHouluobo. You can do it too!" # Index 0 print(main_string[0]) # Index 1 print(main_string[1]) # Check if Index 1 is whitespace print(main_string[1].isspace()) # Slicing 1 print(main_string[0:11]) # Slicing 2: print(main_string[-18:]) # Slicing and concatenation print(main_string[0:11] + ". " + main_string[-18:])
I True I learned English You can do it too! I learned English. You can do it too!
string = "Apple, Banana, Orange, Blueberry" print(string.split())
['Apple,', 'Banana,', 'Orange,', 'Blueberry']
print(string.split(sep=','))
['Apple', ' Banana', ' Orange', ' Blueberry']
# Notice the whitespace after the comma print(string.split(sep=', '))
['Apple', 'Banana', 'Orange', 'Blueberry']
print(string.split(sep=', ', maxsplit=1)) print(string.split(sep=', ', maxsplit=2))
['Apple', 'Banana, Orange, Blueberry'] ['Apple', 'Banana', 'Orange, Blueberry']
str.splitlines(keepends=False)： 有时我们想处理一个在边界处具有不同换行符（'n'、nn'、'r'、'rn'）的语料库。我们要拆分成句子，而不是单个单词。可以使用 splitline 方法来执行此操作。当 keepends=True 时，文本中包含换行符；否则它们被排除在外
import nltk# You may have to `pip install nltk` to use this library.
macbeth = nltk.corpus.gutenberg.raw('shakespeare-macbeth.txt')
print(macbeth.splitlines(keepends=True)[:5]
Output:
['[The Tragedie of Macbeth by William Shakespeare 1603]n', 'n', 'n', 'Actus Primus. Scoena Prima.n', 'n']
str.strip([chars])： 我们使用 strip 方法从字符串的两侧删除尾随空格或字符。例如：
string = "Apple Apple Apple no apple in the box apple apple "
stripped_string = string.strip()
print(stripped_string)
left_stripped_string = (
stripped_string
.lstrip('Apple')
.lstrip()
.lstrip('Apple')
.lstrip()
.lstrip('Apple')
.lstrip()
)
print(left_stripped_string)
capitalized_string = left_stripped_string.capitalize()
print(capitalized_string)
right_stripped_string = (
capitalized_string
.rstrip('apple')
.rstrip()
.rstrip('apple')
.rstrip()
)
print(right_stripped_string)
Output:
Apple Apple Apple no apple in the box apple apple no apple in the box apple apple No apple in the box apple apple No apple in the box
在上面的代码片段中，我们使用了 lstrip 和 rstrip 方法，它们分别从字符串的左侧和右侧删除尾随空格或字符。我们还使用了 capitalize 方法，它将字符串转换为句子大小写str.zfill(width)： zfill 方法用 0 前缀填充字符串以获得指定的宽度。例如：
example = "0.8"# len(example) is 3 example_zfill = example.zfill(5) # len(example_zfill) is 5 print(example_zfill)
Output:
000.8
str.isalpha()： 如果字符串中的所有字符都是字母，该方法返回True；否则返回 False：
# Alphabet string alphabet_one = "Learning" print(alphabet_one.isalpha()) # Contains whitspace alphabet_two = "Learning Python" print(alphabet_two.isalpha()) # Contains comma symbols alphabet_three = "Learning," print(alphabet_three.isalpha())
Output:
True False False
如果字符串字符是字母数字，str.isalnum() 返回 True；如果字符串字符是十进制，str.isdecimal() 返回 True；如果字符串字符是数字，str.isdigit() 返回 True；如果字符串字符是数字，则 str.isnumeric() 返回 True
如果字符串中的所有字符都是小写，str.islower() 返回 True；如果字符串中的所有字符都是大写，str.isupper() 返回 True；如果每个单词的首字母大写，str.istitle() 返回 True：
# islower() example string_one = "Artificial Neural Network" print(string_one.islower()) string_two = string_one.lower()# converts string to lowercase print(string_two.islower()) # isupper() example string_three = string_one.upper() # converts string to uppercase print(string_three.isupper()) # istitle() example print(string_one.istitle())
Output:
False True True True
str.endswith(suffix) 返回 True 是以指定后缀结尾的字符串。如果字符串以指定的前缀开头，str.startswith(prefix) 返回 True：
sentences = ['Time to master data science', 'I love statistical computing', 'Eat, sleep, code']
# endswith() example
for one_sentence in sentences:
print(one_sentence.endswith(('science', 'computing', 'Code')))
Output:
True True False
# startswith() example
for one_sentence in sentences:
print(one_sentence.startswith(('Time', 'I ', 'Ea')))
Output:
True True True
str.find(substring) 如果子字符串存在于字符串中，则返回最低索引；否则它返回 -1。str.rfind(substring) 返回最高索引。如果找到，str.index(substring) 和 str.rindex(substring) 也分别返回子字符串的最低和最高索引。如果字符串中不存在子字符串，则会引发 ValueError
string = "programming"
# find() and rfind() examples
print(string.find('m'))
print(string.find('pro'))
print(string.rfind('m'))
print(string.rfind('game'))
# index() and rindex() examples
print(string.index('m'))
print(string.index('pro'))
print(string.rindex('m'))
print(string.rindex('game'))
Output:
6
0
7
-1
6
0
7
---------------------------------------------------------------------------
ValueErrorTraceback (most recent call last)
~AppDataLocalTemp/ipykernel_11336/3954098241.py in
11 print(string.index('pro'))# Output: 0
12 print(string.rindex('m'))# Output: 7
---> 13 print(string.rindex('game'))# Output: ValueError: substring not found
ValueError: substring not found
str.maketrans(dict_map) 从字典映射创建一个翻译表，str.translate(maketrans) 用它们的新值替换翻译中的元素。例如：
example = "abcde"
mapped = {'a':'1', 'b':'2', 'c':'3', 'd':'4', 'e':'5'}
print(example.translate(example.maketrans(mapped)))
Output:
12345
字符串是可迭代的，因此它们支持使用 for 循环和枚举的循环操作：
# For-loop example word = "bank" for letter in word: print(letter)
Output:
b a n k
# Enumerate example for idx, value in enumerate(word): print(idx, value)
Output:
0 b 1 a 2 n 3 k
当使用关系运算符（>、<、== 等）比较两个字符串时，两个字符串的元素按其 ASCII 十进制数字逐个索引进行比较。例如：
print('a' > 'b')
print('abc' > 'b')
Output:
False False
在这两种情况下，输出都是 False。关系运算符首先比较两个字符串的索引 0 上元素的 ASCII 十进制数。由于 b 大于 a，因此返回 False；在这种情况下，其他元素的 ASCII 十进制数字和字符串的长度无关紧要
当字符串长度相同时，它比较从索引 0 开始的每个元素的 ASCII 十进制数，直到找到具有不同 ASCII 十进制数的元素。例如：
print('abd' > 'abc')
Output:
True
in 运算符用于检查子字符串是否是字符串的成员：
print('data' in 'dataquest')
print('gram' in 'programming')
Output:
True True
检查字符串成员资格、替换子字符串或匹配模式的另一种方法是使用正则表达式
import re substring = 'gram' string = 'programming' replacement = '1234' # Check membership print(re.search(substring, string)) # Replace string print(re.sub(substring, replacement, string))
Output:
pro1234ming
f-string 和 str.format() 方法用于格式化字符串。两者都使用大括号 {} 占位符。例如：
monday, tuesday, wednesday = "Monday", "Tuesday", "Wednesday"
format_string_one = "{} {} {}".format(monday, tuesday, wednesday)
print(format_string_one)
format_string_two = "{2} {1} {0}".format(monday, tuesday, wednesday)
print(format_string_two)
format_string_three = "{one} {two} {three}".format(one=tuesday, two=wednesday, three=monday)
print(format_string_three)
format_string_four = f"{monday} {tuesday} {wednesday}"
print(format_string_four)
Output:
Monday Tuesday Wednesday Wednesday Tuesday Monday Tuesday Wednesday Monday Monday Tuesday Wednesday
f-strings 更具可读性，并且它们比 str.format() 方法实现得更快。因此，f-string 是字符串格式化的首选方法
撇号 (') 在 Python 中表示一个字符串。为了让 Python 知道我们不是在处理字符串，我们必须使用 Python 转义字符 ()。因此撇号在 Python 中表示为 '。与处理撇号不同，Python 中有很多处理引号的方法。它们包括以下内容：
# 1. Represent string with single quote (`""`) and quoted statement with double quote (`""`)
quotes_one ='"Friends don't let friends use minibatches larger than 32" - Yann LeCun'
print(quotes_one)
# 2. Represent string with double quote `("")` and quoted statement with escape and double quote `("statement")`
quotes_two =""Friends don't let friends use minibatches larger than 32" - Yann LeCun"
print(quotes_two)
# 3. Represent string with triple quote `("""""")` and quoted statment with double quote ("")
quote_three = """"Friends don't let friends use minibatches larger than 32" - Yann LeCun"""
print(quote_three)
Output:
"Friends don't let friends use minibatches larger than 32" - Yann LeCun "Friends don't let friends use minibatches larger than 32" - Yann LeCun "Friends don't let friends use minibatches larger than 32" - Yann LeCun
字符串作为编程语言当中最为常见的数据类型，熟练而灵活的掌握其各种属性和方法，实在是太重要了，小伙伴们千万要实时温习，处处留心哦！
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