如何使用Python从JSON数组中删除元素？
如何使用Python从JSON数组中删除元素？
提问于 2021-05-11 19:16:14
我目前正试图为我的高中制作一个Chromebook租赁应用程序，该应用程序将结帐信息存储在JSON文件中。除了从JSON数组中删除数据外，一切都正常工作。我找到了一个YouTube视频(链接)，我认为它可以作为一种解决方案，所以我就跟着做了。但是，每当有两个以上的元素时，我输入任何高于两个的元素，它都不会删除任何内容。更糟糕的是，当我输入第一个时，它会删除除零索引之外的所有内容(每当数组中有两个以上的元素时)。
下面是Python代码：
def view_data(): # Prints JSON Array to screen
with open(filename, "r") as f:
data = json.load(f)
i = 0
for item in data:
name = item["name"]
chromebook = item["chromebook"]
check_out = item["time&date"]
print(f"Index Number: {i}")
print(f"Name : {name}")
print(f"Chromebook : {chromebook}")
print(f"Time Of Checkout: {check_out} ")
print("\n\n")
i = i + 1
def delete_data(): # Deletes an element from the array
view_data()
new_data = []
with open(filename, "r") as f:
data = json.load(f)
data_length = len(data) - 1
print("Which index number would you like to delete?")
delete_option = input(f"Select a number 0-{data_length}: ")
i = 0
for entry in data:
if i == int(delete_option):
pass
i = + 1
else:
new_data.append(entry)
i = + 1
with open(filename, "w") as f:
json.dump(new_data, f, indent=4)以下是JSON文件代码：
[
{
"name": "Tyler",
"chromebook": "12123223",
"time&date": "Check Out Time: 13:33:22 May-11-2021"
},
{
"name": "Craig",
"chromebook": "41222224",
"time&date": "Check Out Time: 13:33:34 May-11-2021"
},
{
"name": "Bill",
"chromebook": "3235223",
"time&date": "Check Out Time: 13:33:46 May-11-2021"
}
]例如，假设用户希望删除JSON数组中的第二个索引。是否有更好的方法在我的Python脚本中实现这一点？
我仍然是一个相当新的学习Python开发人员，如果有更好的解决方案，我是开放的建议。如果你需要信息，我会很活跃的。
回答 3
Stack Overflow用户
回答已采纳
发布于 2021-05-11 19:30:43
第一个问题
但是，每当有两个以上的元素时，我输入任何高于两个的元素，它都不会删除任何内容。更糟糕的是，当我输入第一个时，它会删除除零索引之外的所有内容(每当数组中有两个以上的元素时)。
在delete_data()中，有两行代码读取i = + 1，它只将+1 (即1)指定给i。因此，你永远不会增加你的索引。您可能打算编写i = i+1或i += 1。
def delete_data(): # Deletes an element from the array
view_data()
new_data = []
with open(filename, "r") as f:
data = json.load(f)
data_length = len(data) - 1
print("Which index number would you like to delete?")
delete_option = input(f"Select a number 0-{data_length}: ")
i = 0
for entry in data:
if i == int(delete_option):
i += 1 # <-- here
else:
new_data.append(entry)
i += 1 # <-- and here
with open(filename, "w") as f:
json.dump(new_data, f, indent=4)第二个问题:进一步改进
是否有更好的方法在我的Python脚本中实现这一点？
首先，您可以使用内置的i生成器手动增加enumerate。其次，您可以通过提供参数使函数可重用--代码示例中的文件名来自何处？
# view_data() should probably receive `filename` as a parameter
def view_data(filename: str): # Prints JSON Array to screen
with open(filename, "r") as f:
data = json.load(f)
# iterate over i and data simultaneously
# alternatively, you could just remove i
for i, item in enumerate(data):
name = item["name"]
chromebook = item["chromebook"]
check_out = item["time&date"]
print(f"Index Number: {i}")
print(f"Name : {name}")
print(f"Chromebook : {chromebook}")
print(f"Time Of Checkout: {check_out} ")
print("\n\n")
# not needed anymore: i = i + 1
# view_data() should probably receive `filename` as a parameter
def delete_data(filename: str): # Deletes an element from the array
view_data()
new_data = []
with open(filename, "r") as f:
data = json.load(f)
data_length = len(data) - 1
print("Which index number would you like to delete?")
delete_option = input(f"Select a number 0-{data_length}: ")
# iterate over i and data simultaneously
for i, entry in enumerate(data):
if i != int(delete_option):
new_data.append(entry)
with open(filename, "w") as f:
json.dump(new_data, f, indent=4)此外，你可以用一个列表理解来代替for-循环，有些人可能会认为它更"pythonic"：
new_data = [entry for i, entry in enumerate(data) if i != int(delete_option)]Stack Overflow用户
发布于 2021-05-11 19:34:38
有更简单的方法可以按索引从Python列表中删除元素。
给定li = ["a", "b", "c"]，您可以(至少)通过以下方式按索引删除元素1 ("b")：
li.pop(1) # pop takes an index (defaults to last) and removes and returns the element at that index
del li[1] # the del keyword will also remove an element from a list下面是一些更新的代码：
def view_data(): # Prints JSON Array to screen
with open(filename, "r") as f:
data = json.load(f)
i = 0
for item in data:
name = item["name"]
chromebook = item["chromebook"]
check_out = item["time&date"]
print(f"Index Number: {i}")
print(f"Name : {name}")
print(f"Chromebook : {chromebook}")
print(f"Time Of Checkout: {check_out} ")
print("\n\n")
i = i + 1
def delete_data(): # Deletes an element from the array
view_data()
with open(filename, "r") as f:
data = json.load(f)
data_length = len(data) - 1
print("Which index number would you like to delete?")
delete_option = input(f"Select a number 0-{data_length}: ")
del data[int(delete_option)] # or data.pop(int(delete_option))
with open(filename, "w") as f:
json.dump(data, f, indent=4)Stack Overflow用户
发布于 2021-05-11 19:32:18
import json
data = json.loads(jsonString) #convert json string to object
delete_option = input(f"Select a number 0-{data_length}: ")
del data[int(delete_option)]页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/67493030
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