Python推導式數據處理方式
前言
推導式是一種獨特的數據處理方式,可以快速的從一個數據序列構建另一個新的數據序列的結構體。常用的推導式有一下四種:
- 列表推導式
- 元組推導式
- 集合推導式
- 字典推導式
1、列表推導式
# coding:utf-8 # Author:Yang Xiaopeng """ 語法格式 [表達式 for 變量 in 變量] [表達式 for 變量 in 變量 if 條件表達式] 上述格式中 的 表達式中的變量與for變量一致 """ old_list = [1, 2, 3, 4, 5] new_list = [new_list * new_list for new_list in old_list] # yes [1, 4, 9, 16, 25] # new_list = [new_list1 * new_list for new_list in old_list] # NameError: name 'new_list1' is not defined # new_list = [new_list * new_list for new_list2 in old_list] # NameError: name 'new_list' is not defined old_list = [old_list * old_list for old_list in old_list] # yes [1, 4, 9, 16, 25] print(old_list) print(new_list) new_list = [old_list for old_list in old_list if old_list%2 == 1] # yes [1, 9, 25] print(new_list)
2、元組推導式
# coding:utf-8 # Author:Yang Xiaopeng """ 語法格式 (表達式 for 變量 in 變量) (表達式 for 變量 in 變量 if 條件表達式) 上述格式中 的 表達式中的變量與for變量一致 """ old_list = (1, 2, 3, 4, 5) new_list = (new_list * new_list for new_list in old_list) # yes 1_4_9_16_25_ # new_list = [new_list1 * new_list for new_list in old_list] # NameError: name 'new_list1' is not defined # new_list = [new_list * new_list for new_list2 in old_list] # NameError: name 'new_list' is not defined old_list = (old_list * old_list for old_list in old_list) # yes 1_4_9_16_25_ for item in new_list: print(item, end="_") print("") for item in old_list: print(item, end="_") print("")
3、集合推導式
# coding:utf-8 # Time:2022/6/28 20:57 # Author:Yang Xiaopeng """ 語法格式 {表達式 for 變量 in 變量} {表達式 for 變量 in 變量 if 條件表達式} 上述格式中 的 表達式中的變量與for變量一致 """ old_list = {1, 2, 3, 4, 5} new_list = {new_list * new_list for new_list in old_list} # yes {1, 4, 9, 16, 25} # new_list = {new_list1 * new_list for new_list in old_list} # NameError: name 'new_list1' is not defined # new_list = {new_list * new_list for new_list2 in old_list} # NameError: name 'new_list' is not defined old_list = {old_list * old_list for old_list in old_list} # yes {1, 4, 9, 16, 25} print(old_list) print(new_list) new_list = {old_list for old_list in old_list if old_list % 2 == 1} # yes {1, 9, 25} print(new_list)
4、字典推導式
# coding:utf-8 # Author:Yang Xiaopeng """ 語法格式 {key : value for key in 變量} {key : value for key in 變量 if 表達式} """ old_dict = ["Zhang", "Wang", "Yang", "Jim"] new_dict = {key:len(key) for key in old_dict} # yes {1, 4, 9, 16, 25} print(old_dict) print(new_dict) new_dict = {lll:len(lll) for lll in old_dict if len(lll) % 2 == 0} # yes {1, 9, 25} print(new_dict)
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