Python中的日期本身不是資料型別，但我們可以匯入一個名為datetime的模組，將日期作為日期物件使用。
import datetime
x = datetime.datetime.now()
print(x)
日期輸出
import datetime
x = datetime.datetime.now()
print(x.year)
print(x.strftime("%A"))
建立日期物件
import datetime
x = datetime.datetime(2020, 5, 17)
print(x)
strftime（）方法
import datetime
x = datetime.datetime(2018, 6, 1)
print(x.strftime("%B"))
| Directive | Description | Example |
|---|---|---|
| %a | Weekday, short version | Wed |
| %A | Weekday, full version | Wednesday |
| %w | Weekday as a number 0-6, 0 is Sunday | 3 |
| %d | Day of month 01-31 | 31 |
| %b | Month name, short version | Dec |
| %B | Month name, full version | December |
| %m | Month as a number 01-12 | 12 |
| %y | Year, short version, without century | 18 |
| %Y | Year, full version | 2018 |
| %H | Hour 00-23 | 17 |
| %I | Hour 00-12 | 05 |
| %p | AM/PM | PM |
| %M | Minute 00-59 | 41 |
| %S | Second 00-59 | 08 |
| %f | Microsecond 000000-999999 | 548513 |
| %z | UTC offset | +0100 |
| %Z | Timezone | CST |
| %j | Day number of year 001-366 | 365 |
| %U | Week number of year, Sunday as the first day of week, 00-53 | 52 |
| %W | Week number of year, Monday as the first day of week, 00-53 | 52 |
| %c | Local version of date and time | Mon Dec 31 17:41:00 2018 |
| %C | Century | 20 |
| %x | Local version of date | 12/31/18 |
| %X | Local version of time | 17:41:00 |
| %% | A % character | % |
| %G | ISO 8601 year | 2018 |
| %u | ISO 8601 weekday (1-7) | 1 |
min（）和max（）函數可用於查詢可迭代中的最低或最高值
x = min(5, 10, 25)
y = max(5, 10, 25)
print(x)
print(y)
函數的作用是：返回指定數位的絕對（正）值
x = abs(-7.25)
print(x)
pow（x，y）函數將x的值返回到y（xy）的冪。
# Return the value of 4 to the power of 3 (same as 4 * 4 * 4)
x = pow(4, 3)
print(x)
數學模組
import math
x = math.sqrt(64)
print(x)
ceil（）方法將一個數位向上舍入到其最接近的整數，然後進行數學運算。floor（）方法將數位向下舍入到最接近的整數，並返回結果
import math
x = math.ceil(1.4)
y = math.floor(1.4)
print(x) # returns 2
print(y) # returns 1
pi常數，返回pi的值（3.14…）
import math
x = math.pi
print(x)
從JSON轉換為Python
import json
# some JSON:
x = '{ "name":"John", "age":30, "city":"New York"}'
# parse x:
y = json.loads(x)
# the result is a Python dictionary:
print(y["age"])
從Python轉換為JSON
import json
# a Python object (dict):
x = {
"name": "John",
"age": 30,
"city": "New York"
}
# convert into JSON:
y = json.dumps(x)
# the result is a JSON string:
print(y)
您可以將以下型別的Python物件轉換為JSON字串.
當您從Python轉換為JSON時，Python物件將轉換成JSON（JavaScript）等價物
| Python | JSON |
|---|---|
| dict | Object |
| list | Array |
| tuple | Array |
| str | String |
| int | Number |
| float | Number |
| True | true |
| False | false |
| None | null |
格式化結果
使用縮排引數定義縮排的數量
json.dumps(x, indent=4)
您還可以定義分隔符，預設值為（「，」，「：」，這意味著使用逗號和空格分隔每個物件，使用冒號和空格分隔鍵和值
json.dumps(x, indent=4, separators=(". ", " = "))
json_dumps（）方法有引數來對resu中的鍵進行排序
json.dumps(x, indent=4, sort_keys=True)
Python有一個名為re的內建包，可用於處理正規表示式。
import re
正規表示式函數
| Function | Description |
|---|---|
| findall | Returns a list containing all matches |
| search | Returns a Match object if there is a match anywhere in the string |
| split | Returns a list where the string has been split at each match |
| sub | Replaces one or many matches with a string |
元字元是具有特殊含義的字元
| Character | Description | Example |
|---|---|---|
| [] | A set of characters | "[a-m]" |
| \ | Signals a special sequence (can also be used to escape special characters) | "\d" |
| . | Any character (except newline character) | "he..o" |
| ^ | Starts with | "^hello" |
| $ | Ends with | "planet$" |
| * | Zero or more occurrences | "he.*o" |
| + | One or more occurrences | "he.+o" |
| ? | Zero or one occurrences | "he.?o" |
| {} | Exactly the specified number of occurrences | "he.{2}o" |
| | | Either or | "falls|stays" |
| () | Capture and group |
特殊序列
| Character | Description | Example |
|---|---|---|
| \A | Returns a match if the specified characters are at the beginning of the string | "\AThe" |
| \b | Returns a match where the specified characters are at the beginning or at the end of a word (the "r" in the beginning is making sure that the string is being treated as a "raw string") | r"\bain" r"ain\b" |
| \B | Returns a match where the specified characters are present, but NOT at the beginning (or at the end) of a word (the "r" in the beginning is making sure that the string is being treated as a "raw string") | r"\Bain" r"ain\B" |
| \d | Returns a match where the string contains digits (numbers from 0-9) | "\d" |
| \D | Returns a match where the string DOES NOT contain digits | "\D" |
| \s | Returns a match where the string contains a white space character | "\s" |
| \S | Returns a match where the string DOES NOT contain a white space character | "\S" |
| \w | Returns a match where the string contains any word characters (characters from a to Z, digits from 0-9, and the underscore _ character) | "\w" |
| \W | Returns a match where the string DOES NOT contain any word characters | "\W" |
| \Z | Returns a match if the specified characters are at the end of the string | "Spain\Z" |
集合是一對方括號[]內的一組字元，具有特殊含義
| Set | Description |
|---|---|
| [arn] | Returns a match where one of the specified characters (a, r, or n) is present |
| [a-n] | Returns a match for any lower case character, alphabetically between a and n |
| [^arn] | Returns a match for any character EXCEPT a, r, and n |
| [0123] | Returns a match where any of the specified digits (0, 1, 2, or 3) are present |
| [0-9] | Returns a match for any digit between 0 and 9 |
| [0-5][0-9] | Returns a match for any two-digit numbers from 00 and 59 |
| [a-zA-Z] | Returns a match for any character alphabetically between a and z, lower case OR upper case |
| [+] | In sets, +, *, ., ` |
findall()函數的作用是：返回一個包含所有匹配項的列表。
import re
txt = "The rain in Spain"
x = re.findall("ai", txt)
print(x)
該列表按找到的順序包含匹配項。
如果未找到匹配項，則返回空列表
import re
txt = "The rain in Spain"
x = re.findall("Portugal", txt)
print(x)
search()函數的作用是：在字串中搜尋匹配項，如果存在匹配項，則返回匹配物件。
import re
txt = "The rain in Spain"
x = re.search("\s", txt)
print("The first white-space character is located in position:", x.start())
split()函數的作用是：返回一個列表，其中字串在每次匹配時被拆分
import re
txt = "The rain in Spain"
x = re.split("\s", txt)
print(x)
可以通過指定maxsplit引數來控制出現次數
import re
txt = "The rain in Spain"
x = re.split("\s", txt, 1)
print(x)
sub()函數的作用是：用您選擇的文字替換匹配項
import re
txt = "The rain in Spain"
x = re.sub("\s", "9", txt)
print(x) # The9rain9in9Spain
您可以通過指定count引數來控制替換的數量
import re
txt = "The rain in Spain"
x = re.sub("\s", "9", txt, 2)
print(x)
匹配物件是包含有關搜尋和結果的資訊的物件。
注意：如果沒有匹配，將返回值None，而不是match物件。
.span()返回包含匹配的開始位置和結束位置的元組。
import re
txt = "The rain in Spain"
x = re.search(r"\bS\w+", txt)
print(x.span()) # (12, 17)
.string 返回傳遞到函數中的字串
import re
txt = "The rain in Spain"
x = re.search(r"\bS\w+", txt)
print(x.string) # The rain in Spain
.group() 返回字串中存在匹配項的部分
import re
txt = "The rain in Spain"
x = re.search(r"\bS\w+", txt)
print(x.group()) # Spain
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