I have sample code
a=10
print(recent_variable) -- it should print value of a
b=20
print(recent_variable) -- it should print value of b
c = [10,12]
print(recent_variable) -- it should print value of c
d= somfunc()
print(recent_variable) -- it should print value of d
any possible way of doing this
Intead of writing the python variable name in the print i can just put print(some syntax to show the recent variable) and it prints it value`
If you had a very narrow use case in mind you could create your own memoized assignment function that keeps track of the last value assigned through it (see below). As a general solution, of course, that approach would not be appropriate.
Example:
import random
def memo_assign(value):
if not getattr(memo_assign, "last_value", None):
memo_assign.last_value = None
memo_assign.last_value = value
return value
a = memo_assign(10)
print(a, memo_assign.last_value)
b = memo_assign(20)
print(b, memo_assign.last_value)
c = memo_assign([10,12])
print(c, memo_assign.last_value)
d = memo_assign(random.randint(1, 100))
print(d, memo_assign.last_value)
Output:
10 10
20 20
[10, 12] [10, 12]
9 9
Related
I'm trying to get the name of a enum given one of its multiple values:
class DType(Enum):
float32 = ["f", 8]
double64 = ["d", 9]
when I try to get one value giving the name it works:
print DType["float32"].value[1] # prints 8
print DType["float32"].value[0] # prints f
but when I try to get the name out of a given value only errors will come:
print DataType(8).name
print DataType("f").name
raise ValueError("%s is not a valid %s" % (value, cls.name))
ValueError: 8 is not a valid DataType
ValueError: f is not a valid DataType
Is there a way to make this? Or am I using the wrong data structure?
The easiest way is to use the aenum library1, which would look like this:
from aenum import MultiValueEnum
class DType(MultiValueEnum):
float32 = "f", 8
double64 = "d", 9
and in use:
>>> DType("f")
<DType.float32: 'f'>
>>> DType(9)
<DType.double64: 'd'>
As you can see, the first value listed is the canonical value, and shows up in the repr().
If you want all the possible values to show up, or need to use the stdlib Enum (Python 3.4+), then the answer found here is the basis of what you want (and will also work with aenum):
class DType(Enum):
float32 = "f", 8
double64 = "d", 9
def __new__(cls, *values):
obj = object.__new__(cls)
# first value is canonical value
obj._value_ = values[0]
for other_value in values[1:]:
cls._value2member_map_[other_value] = obj
obj._all_values = values
return obj
def __repr__(self):
return '<%s.%s: %s>' % (
self.__class__.__name__,
self._name_,
', '.join([repr(v) for v in self._all_values]),
)
and in use:
>>> DType("f")
<DType.float32: 'f', 8>
>>> Dtype(9)
<DType.float32: 'd', 9>
1 Disclosure: I am the author of the Python stdlib Enum, the enum34 backport, and the Advanced Enumeration (aenum) library.
d =dict(input('Enter a dictionary'))
sum = 0
for i in d.values():
sum +=i
print(sum)
outputs: Enter a dictionary{'a': 100, 'b':200, 'c':300}
this is the problem arises:
Traceback (most recent call last):
File "G:/DurgaSoftPython/smath.py", line 2, in <module>
d =dict(input('Enter a dictionary'))
ValueError: dictionary update sequence element #0 has length 1; 2 is required
You can't create a dict from a string using the dict constructor, but you can use ast.literal_eval:
from ast import literal_eval
d = literal_eval(input('Enter a dictionary'))
s = 0 # don't name your variable `sum` (which is a built-in Python function
# you could've used to solve this problem)
for i in d.values():
s +=i
print(s)
Output:
Enter a dictionary{'a': 100, 'b':200, 'c':300}
600
Using sum:
d = literal_eval(input('Enter a dictionary'))
s = sum(d.values())
print(s)
import json
inp = input('Enter a dictionary')
inp = dict(json.loads(inp))
sum = sum(inp.values())
print(sum)
input Enter a dictionary{"a": 100, "b":200, "c":300}
output 600
Actually the return of input function is a string. So, in order to have a valid python dict you need to evaluate the input string and convert it into dict.
One way to do this can be done using literal_eval from ast package.
Here is an example:
from ast import literal_eval as le
d = le(input('Enter a dictionary: '))
_sum = 0
for i in d.values():
_sum +=i
print(_sum)
Demo:
Enter a dictionary: {'a': 100, 'b':200, 'c':300}
600
PS: Another way can be done using eval but it's not recommended.
I have been trying to take integer inputs seperated by any number of white spaces or line breaks. I know how to take space seperated outputs and outputs having line breaks. In C based languages we don't have to care about where the input is, it automatically takes the input when found, but I don't think this is the case with Python(correct me if I am wrong). Can anybody help?
I tried using a While statement till True and using a try statement in it. But it doesn't work.
a = []
try:
while(True):
a.append(int(input()))
except:
pass
print(a)
when i input
12 12
12
it returns an empty list. If i remove the int in the input it returns a list [12 12, 12].
Try this: The Shortest way possible
a = []
s=input()
while s != '':
i = s.split()
[a.append(int(j)) for j in i]
s=input()
print(a)
Input:
1 2 3
4 5
6
Output:
[1, 2, 3, 4, 5, 6]
You can also try:
a = []
s=input()
while s != '':
i = s.split()
a.extend(map(lambda s: int(s),i))
s=input()
print(a)
Wait, so I think I understand it now. You want to accept any amount of input, but save each input separated by whitespace as its own entry? There is actually a string method for that. Here's an example script for it. It's not the best, but it demonstrates the method pretty well.
list = []
string = "user input goes here"
splitString = string.split()
for word in splitString:
list.append(word)
print(list)
Output:
["user", "input", "goes", "here"]
The string.split() method uses space by default, but you can specify another delimiter like the # sign.
List = []
String = "Hi#my#name#is#bob"
newString = String.split("#")
for word in newString:
list.append(word)
EDIT: Here is a full working implementation that will work whether the thing separating two inputs is whitespace, newlines, or anything else you'd like.
import re
list = []
while True:
string = input()
if string == "break":
break
splitString = re.split("[\s | \r\n]", string)
for word in splitString:
list.append(word)
cleanList = []
for word in list:
if word != '':
cleanList.append(word)
print(cleanList)
Input:
12 94 17
56
3
Output:
[12, 94, 17, 56, 3]
Functional proof: Click here
Hope you will some insight in this example & have added my personal view of how to code.
Firstly, giving input with multi-spaces is understandable but not multi-lines. Prefer taking input one by one.
For testing & debugging purposes, prefer separate collecting user and processing input data.
Now, say you have collected your user input and stored as data using raw_input, which is handy when you need to collect multiline inputs. Please explore raw_input, it is supported in Python3 and Python2.
>>>
>>> data = '''12
...
... 12 12
...
...
... 12'''
>>> data
'12 \n\n12 12\n\n\n12'
>>> print(data)
12
12 12
12
step1: clear all line separations
>>> double_spaces = ' '
>>> single_space = ' '
>>> data = data.strip().replace('\n', single_space)
>>> data
'12 12 12 12'
step2: Fix multiple spaces
>>> while double_spaces in data:
... data = data.replace(double_spaces, single_space)
...
>>> data
'12 12 12 12'
>>> print(list(map(int, data.split()))
...
... )
[12, 12, 12, 12]
>>>
Problems with you code
>>> a = []
>>> try:
... while(True):
... a.append(int(input()))
... except:
... pass
...
12
1
12 12
>>> a
[12, 1]
>>>
When you enter 12 12, below is supposed to happen.
>>> int('12 12')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '12 12'
Since this code had bad exception handling except:, your use case is returning an empty list as expected.
Since I have changed the input, you see this difference.
In Python 3, I want to return the units place of an integer value, then tens, then hundreds and so on. Suppose I have an integer 456, first I want to return 6, then 5 then 4. Is there any way? I tried floor division and for loop but didn't work.
If you look at the list of basic operators from the documentation, for example here,
Operator Description Example
% Modulus Divides left hand operand by right hand operand and returns remainder b % a = 1
// Floor Division - The division of operands where the result is the quotient in which the digits after the decimal point are removed. But if one of the operands is negative, the result is floored, i.e., rounded away from zero (towards negative infinity): 9//2 = 4 and 9.0//2.0 = 4.0, -11//3 = -4, -11.0//3 = -4.0
With that knowledge, you can get what you want as follows:
In [1]: a = 456
In [2]: a % 10
Out[2]: 6
In [3]: (a % 100) // 10
Out[3]: 5
In [4]: a // 100
Out[4]: 4
Write a generator if you want to retrieve digits in different places of your code based on requirement as follows.
If you are not much familiar with Python's generator, have a quick look at https://www.programiz.com/python-programming/generator.
» Here get_digits() is a generator.
def get_digits(n):
while str(n):
yield n % 10
n = n // 10
if not n:
break
digit = get_digits(1729)
print(next(digit)) # 9
print(next(digit)) # 2
print(next(digit)) # 7
print(next(digit)) # 1
» If you wish to iterate over digits, you can also do so as follows.
for digit in get_digits(74831965):
print(digit)
# 5
# 6
# 9
# 1
# 3
# 8
# 4
# 7
» Quick overview about its usage (On Python3's Interactive terminal).
>>> def letter(name):
... for ch in name:
... yield ch
...
>>>
>>> char = letter("RISHIKESH")
>>>
>>> next(char)
'R'
>>>
>>> "Second letter is my name is: " + next(char)
'Second letter is my name is: I'
>>>
>>> "3rd one: " + next(char)
'3rd one: S'
>>>
>>> next(char)
'H'
>>>
I am trying to create a program which creates a Fibonacci sequence up to the value of the sequence being 200. I have the basic set up down where I can compute the sequence but I wish to display it in a certain way and I have forgotten how to achieve this.
I wish to write the numbers to an array which I have defined as empty initially, compute the numbers and assign them to the array and print said array. In my code below the computation is ok but when printed to screen, the array shows the value 233 which is above 200 and not what I'm looking for. I wish to print all the values under 200 which I've stored in an array.
Is there a better way to initially define the array for what I want and what is the correct way to print the array at the end with all elements below 200?
Code follows:
#This program calculates the fibonacci sequence up to the value of 200
import numpy as np
x = np.empty(14, float) #Ideally creates an empty array to deposit the fibonacci numbers in
f = 0.0 #Dummy variable to be edited in the while loop
#Here the first two values of the sequence are defined alongside a counter starting at i = 1
x[0] = 0.0
x[1] = 1.0
i = 1
#While loop which computes the values and writes them to the array x
while f <= 200:
f = x[i]+x[i-1] #calculates the sequence element
i += 1 #Increases the iteration counter by 1 for each loop
x[i] = f #set the array element equal to the calculated sequence number
print(x)
For reference here is a quick terminal output, Ideally I wish to remove the last element:
[ 0. 1. 1. 2. 3. 5. 8. 13. 21. 34. 55. 89.
144. 233.]
There are a number of stylistic points here. Firstly, you should probably use integers, rather than floats. Secondly, you should simply append each number to a list, rather than pre-define an array of a particular size.
Here's an interactive session:
>>> a=[0,1]
>>> while True:
b=a[-1]+a[-2]
if b<=200:
a.append(b)
else:
break
>>> a
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144]
Here is a way without using indices:
a = 0
x = [a]
b = 1
while b <= 200:
x.append(b)
a, b = b, a+b
print(x)