Python在程式語言流行指數PYPL中已多次排名第一。
由於其程式碼可讀性和更簡單的語法,它被認為是有史以來最簡單的語言。
NumPy、Pandas、TensorFlow等各種AI和機器學習庫的豐富性,是Python核心需求之一。
如果你是資料科學家或 AI/機器學習的初學者,那麼Python是開始你的旅程的正確選擇。
本次,小F會帶著大家探索一些Python程式設計的基礎知識,雖然簡單但都很有用。
字串運算
正規表示式
1、資料型別
下面是Python中的各種資料類型。
2、變數變數名稱不能以數字開頭
變數名只能包含字母數字字元和底線(A-z、0-9和_)
變數名稱區分大小寫(age、Age和AGE是三個不同的變數)var1 = 'Hello World' var2 = 16 _unuseful = 'Single use variables'
#輸出結果如下。
3、列表列表(List)是一種有序且可更改的集合,允許重複的成員。 它可能不是同質的,我們可以建立一個包含不同資料類型(如整數、字串和物件)的清單。 >>> companies = ["apple","google","tcs","accenture"] >>> print(companies) ['apple', 'google', 'tcs', 'accenture'] >>> companies.append("infosys") >>> print(companies) ['apple', 'google', 'tcs', 'accenture', 'infosys'] >>> print(len(companies)) 5 >>> print(companies[2]) tcs >>> print(companies[-2]) accenture >>> print(companies[1:]) ['google', 'tcs', 'accenture', 'infosys'] >>> print(companies[:1]) ['apple'] >>> print(companies[1:3]) ['google', 'tcs'] >>> companies.remove("infosys") >>> print(companies) ["apple","google","tcs","accenture"] >>> companies.pop() >>> print(companies) ["apple","google","tcs"]
>>> set1 = {1,2,3,7,8,9,3,8,1} >>> print(set1) {1, 2, 3, 7, 8, 9} >>> set1.add(5) >>> set1.remove(9) >>> print(set1) {1, 2, 3, 5, 7, 8} >>> set2 = {1,2,6,4,2} >>> print(set2) {1, 2, 4, 6} >>> print(set1.union(set2))# set1 | set2 {1, 2, 3, 4, 5, 6, 7, 8} >>> print(set1.intersection(set2)) # set1 & set2 {1, 2} >>> print(set1.difference(set2)) # set1 - set2 {8, 3, 5, 7} >>> print(set2.difference(set1)) # set2 - set1 {4, 6}
>>> # example 1 >>> user = { 'username': 'Fan', 'age': 20, 'mail_id': 'codemaker2022@qq.com', 'phone': '18650886088' } >>> print(user) {'mail_id': 'codemaker2022@qq.com', 'age': 20, 'username': 'Fan', 'phone': '18650886088'} >>> print(user['age']) 20 >>> for key in user.keys(): >>> print(key) mail_id age username phone >>> for value in user.values(): >>>print(value) codemaker2022@qq.com 20 Fan 18650886088 >>> for item in user.items(): >>>print(item) ('mail_id', 'codemaker2022@qq.com') ('age', 20) ('username', 'Fan') ('phone', '18650886088') >>> # example 2 >>> user = { >>> 'username': "Fan", >>> 'social_media': [ >>> { >>> 'name': "Linkedin", >>> 'url': "https://www.linkedin.com/in/codemaker2022" >>> }, >>> { >>> 'name': "Github", >>> 'url': "https://github.com/codemaker2022" >>> }, >>> { >>> 'name': "QQ", >>> 'url': "https://codemaker2022.qq.com" >>> } >>> ], >>> 'contact': [ >>> { >>> 'mail': [ >>> "mail.Fan@sina.com", >>> "codemaker2022@qq.com" >>> ], >>> 'phone': "18650886088" >>> } >>> ] >>> } >>> print(user) {'username': 'Fan', 'social_media': [{'url': 'https://www.linkedin.com/in/codemaker2022', 'name': 'Linkedin'}, {'url': 'https://github.com/codemaker2022', 'name': 'Github'}, {'url': 'https://codemaker2022.qq.com', 'name': 'QQ'}], 'contact': [{'phone': '18650886088', 'mail': ['mail.Fan@sina.com', 'codemaker2022@qq.com']}]} >>> print(user['social_media'][0]['url']) https://www.linkedin.com/in/codemaker2022 >>> print(user['contact']) [{'phone': '18650886088', 'mail': ['mail.Fan@sina.com', 'codemaker2022@qq.com']}]
# 定义用户年龄 age = 27 dob = '16/12/1994' # 定义用户生日多行註釋,用特殊引號(""")括起來,你可以將訊息放在多行中。
""" Python小常识 This is a multi line comment """7、基本功能print ()函數在控制台中列印提供的訊息。此外你也可以提供檔案或緩衝區輸入作為在螢幕上列印的參數。
print(object(s), sep=separator, end=end, file=file, flush=flush) print("Hello World") # prints Hello World print("Hello", "World")# prints Hello World? x = ("AA", "BB", "CC") print(x) # prints ('AA', 'BB', 'CC') print("Hello", "World", sep="---") # prints Hello---Worldinput()函數用來收集來自控制台的使用者輸入。 這裡需要注意,input()會把你輸入的任何內容轉換為字串。因此,如果你將年齡作為整數值提供,但input()方法將其作為字串傳回,此時就需要手動將其轉換為整數。
>>> name = input("Enter your name: ") Enter your name: Codemaker >>> print("Hello", name) Hello Codemaker
>>> str1 = "Hello World" >>> print("The length of the stringis ", len(str1)) The length of the stringis 11str()用於將其他資料類型轉換為字串值。
>>> str(123) 123 >>> str(3.14) 3.14int()用於將字串轉換為整數。
>>> int("123") 123 >>> int(3.14) 38、條件語句條件語句是用來根據特定條件更改程式流程的程式碼區塊。這些語句只有在滿足特定條件時才會執行。在Python中,我們使用if,if- else,循環(for,while)作為條件語句根據某些條件來改變程式的流程。if-else語句。
>>> num = 5 >>> if (num > 0): >>>print("Positive integer") >>> else: >>>print("Negative integer")elif語句。
>>> name = 'admin' >>> if name == 'User1': >>> print('Only read access') >>> elif name == 'admin': >>> print('Having read and write access') >>> else: >>> print('Invalid user') Having read and write access9 、循環語句迴圈是一個條件語句,用來重複某些語句(在其主體中),直到滿足某個條件。在Python中,我們通常使用for和while循環。for循環。
>>> # loop through a list >>> companies = ["apple", "google", "tcs"] >>> for x in companies: >>> print(x) apple google tcs >>> # loop through string >>> for x in "TCS": >>>print(x) T C Srange()函數傳回一個數字序列,它可以用作for循環控制。它基本上需要三個參數,其中第二個和第三個是可選的。參數是開始值、停止值和步進數。步進數是每次迭代循環變數的增量值。
>>> # loop with range() function >>> for x in range(5): >>>print(x) 0 1 2 3 4 >>> for x in range(2, 5): >>>print(x) 2 3 4 >>> for x in range(2, 10, 3): >>>print(x) 2 5 8我們也可以使用else關鍵字在循環結束時執行一些語句。######在循環結束時提供else語句以及循環結束時需要執行的語句。###
>>> for x in range(5): >>>print(x) >>> else: >>>print("finished") 0 1 2 3 4 finished###while循環。###
>>> count = 0 >>> while (count < 5): >>>print(count) >>>count = count + 1 0 1 2 3 4###我們可以在while循環的末尾使用else,類似於for循環,當條件為假時執行一些語句。###
>>> count = 0 >>> while (count < 5): >>>print(count) >>>count = count + 1 >>> else: >>>print("Count is greater than 4") 0 1 2 3 4 Count is greater than 4
函数是用于执行任务的可重用代码块。在代码中实现模块化并使代码可重用,这是非常有用的。
>>> # This prints a passed string into this function >>> def display(str): >>>print(str) >>>return >>> display("Hello World") Hello World
即使语句在语法上是正确的,它也可能在执行时发生错误。这些类型的错误称为异常。我们可以使用异常处理机制来避免此类问题。
在Python中,我们使用try,except和finally关键字在代码中实现异常处理。
>>> def divider(num1, num2): >>> try: >>> return num1 / num2 >>> except ZeroDivisionError as e: >>> print('Error: Invalid argument: {}'.format(e)) >>> finally: >>> print("finished") >>> >>> print(divider(2,1)) >>> print(divider(2,0)) finished 2.0 Error: Invalid argument: division by zero finished None
字符串是用单引号或双引号(',")括起来的字符集合。
我们可以使用内置方法对字符串执行各种操作,如连接、切片、修剪、反转、大小写更改和格式化,如split()、lower()、upper()、endswith()、join()和ljust()、rjust()、format()。
>>> msg = 'Hello World' >>> print(msg) Hello World >>> print(msg[1]) e >>> print(msg[-1]) d >>> print(msg[:1]) H >>> print(msg[1:]) ello World >>> print(msg[:-1]) Hello Worl >>> print(msg[::-1]) dlroW olleH >>> print(msg[1:5]) ello >>> print(msg.upper()) HELLO WORLD >>> print(msg.lower()) hello world >>> print(msg.startswith('Hello')) True >>> print(msg.endswith('World')) True >>> print(', '.join(['Hello', 'World', '2022'])) Hello, World, 2022 >>> print(' '.join(['Hello', 'World', '2022'])) Hello World 2022 >>> print("Hello World 2022".split()) ['Hello', 'World', '2022'] >>> print("Hello World 2022".rjust(25, '-')) ---------Hello World 2022 >>> print("Hello World 2022".ljust(25, '*')) Hello World 2022********* >>> print("Hello World 2022".center(25, '#')) #####Hello World 2022#### >>> name = "Codemaker" >>> print("Hello %s" % name) Hello Codemaker >>> print("Hello {}".format(name)) Hello Codemaker >>> print("Hello {0}{1}".format(name, "2022")) Hello Codemaker2022
>>> import re >>> phone_num_regex = re.compile(r'ddd-ddd-dddd') >>> mob = phone_num_regex.search('My number is 996-190-7453.') >>> print('Phone number found: {}'.format(mob.group())) Phone number found: 996-190-7453 >>> phone_num_regex = re.compile(r'^d+$') >>> is_valid = phone_num_regex.search('+919961907453.') is None >>> print(is_valid) True >>> at_regex = re.compile(r'.at') >>> strs = at_regex.findall('The cat in the hat sat on the mat.') >>> print(strs) ['cat', 'hat', 'sat', 'mat']
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