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python
A. Vreeswijk
A. Vreeswijk

Reputation: 954

Python Set all dictionary values to lower case with specific key

I have a problem. I want to set all the values from my dictionary that are connected with the ["key1"] to lowercase. I started to create a test dictionary:

# Define test devices
item1 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}

item2 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}

collection = []
collection.append(item1)
collection.append(item2)

After that, I started by tring to set every value to lowercase like this:

for item in collection:
    item = dict((k, v.lower()) for k,v in item.items())

But after that, I printed the collection, but nothing changed. Why are all my values not lowercase and how can I set it for a specific key?

Upvotes: 0

Views: 1898

Answers (8)

Arvind Kumar
Arvind Kumar

Reputation: 451

You can update the list using the below code:

for item in collection:
    item.update(dict((k, v.lower()) for k,v in item.items() if k=='key1'))
print(collection)

Output

[{'key1': 'value1', 'key2': 'VALUE2'}, {'key1': 'value1', 'key2': 'VALUE2'}]

Upvotes: 0

Juan
Juan

Reputation: 54

There is just a little problem of misconception in how updating a dictionary works. You are trying to use the item coming out of the for, while this is just a copy of the original. You could just use the key to refer to the item in the originnal dictionnary and update it:

# Define test devices
item1 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}

item2 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}

collection = []
collection.append(item1)
collection.append(item2)

for item in collection:
    for k,v in item.items():
        if k == "key1":
            item[k] = v.lower()

print(collection)

Upvotes: 0

user13824946
user13824946

Reputation:

help your self with this approach

item1 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
} 

for k, v in item1.items():
  if k == 'key1':
    item1.update({k:v.lower()})
    print(item1)

output

{'key1': 'value1', 'key2': 'VALUE2'}

Upvotes: 1

Aman Neo
Aman Neo

Reputation: 223

Here added an extra piece of code

for i in collection:
    i["key1"] = i["key1"].lower()

Here is the file

item1 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}

item2 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}
collection = []
collection.append(item1)
collection.append(item2)

print("Before operation",collection)

for i in collection:
    i["key1"] = i["key1"].lower()

print("After Operation",collection)

Output
enter image description here

Upvotes: 0

Chris
Chris

Reputation: 300

Here is a working example

# Define test devices
item1 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}

item2 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}

collection = (item1,item2)

for item in collection:
    for k,v in item.items():
        item[k] = v.lower()

Upvotes: 0

Shubhashish
Shubhashish

Reputation: 64

for item in collection:
   for key in item:
    if key=="key1":
        item[key]=item[key].lower()

Why?

In python, strings are immutable. When you use string.lower(), you create a copy of the original string and turn all the characters into lowercases. Hence you need the key to point to the new string. Unless you reassign the new string, the old string would not be replaced.

Upvotes: 0

Salim Baskoy
Salim Baskoy

Reputation: 719

   item1 = {
    "key1": "VALUE1",
    "key2": "VALUE2"
}
for key, value in item1.items():
  item1[key]=value.lower()

print(item1)

output {'key1': 'value1', 'key2': 'value2'}

Upvotes: 0

Melvin Abraham
Melvin Abraham

Reputation: 3036

When using for loop with dictionary, you iterate through the keys present in it. All you need to do is assign to the corresponding key using dictionary[key] = .... The dictionary[key] in the right-hand side fetches the value associated with the key upon which you may call the lower() function.

This will fix the issue:

for key in dictionary:
    dictionary[key] = dictionary[key].lower()

Upvotes: 1

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