Python使用正则表达式在字符串foo：之后提取数字

Question

I have data like this: {"address": "1GocfVCWTiRViPtqZetcX4UiCxnKxgTHwK", "balance": 1234, "pending_balance": 0, "paid_out": 0}

I want extract numbers after balance, but its can be from 0 to infinity.

So, from example above the output desired:

1234

And btw one more question. I have got data like this {"address": "1GocfVCWTiRViPtqZetcX4UiCxnKxgTHwK", "invoice": "invNrKU2ZFMuAJKUiejyVe3X34ybP9awyWZBfUEdY2dZKxYTB8ajW", "redeem_code": "BTCvQDD9xFYHHDYNi1JYeLY1eEkGFBFB49qojETjLBZ2CVYyPm56B"} Whats the normal way of doing that:

strs = repr(s)  
address = s[13:47]
invoice = s[62:115]
redeem_code = s[134:187]
print(address)
print(invoice)
print(redeem_code)

Thx for help.

Answer 1

don't ever use regexes to parse structured data like this. Once parsed with proper means ( json.loads or ast.literal_eval both work here), they become native python structure, trivial to access to.

In your case, using json.loads in one line:

import json

print(json.loads('{"address": "1GocfVCWTiRViPtqZetcX4UiCxnKxgTHwK", "balance": 1234, "pending_balance": 0, "paid_out": 0}')["balance"])

result:

1234

(same method applies for your second question)

Answer 2

Actually what you are showing us is what in Python is called a dictionary. That is a set of key and values.

Look here for more info: https://docs.python.org/3.6/tutorial/datastructures.html#dictionaries

Your dictionary has the following keys and values:

"address" --> "1GocfVCWTiRViPtqZetcX4UiCxnKxgTHwK"
"balance" --> 1234
"pending_balance" --> 0
"paid_out" --> 0

Now if what you have is a dictionary:

d = {"address": "1GocfVCWTiRViPtqZetcX4UiCxnKxgTHwK", "balance": 1234, "pending_balance": 0, "paid_out": 0}

print(d.get('balanace')) #1234

If however what you have is an external file with that information or you got it from a web service of some sort, you have a string representation of a dictionary. Here is where the JSON-library becomes valuable:

import json

# Assuming you got a string
s = '{"address": "1GocfVCWTiRViPtqZetcX4UiCxnKxgTHwK", "balance": 1234, "pending_balance": 0, "paid_out": 0}'
d = json.loads(s) # <-- converts the string to a dictionary

print(d.get('balance')) #1234

Answer 3

Your data looks like json, so the preferable way of dealing with it is parsing using json module

import json
parsed_data = json.loads(data)
balance = parsed_data['balance']

If using regular expressions is a must, you can use following code

import re
match = re.search('"balance": (\d+)', data)
balance = int(match.group(1))

In this example me use \\d+ to match string of digits and parenthesis to create a group. Group 0 would be the whole matched string and group 1 - the first group we created.