CODEWITHSUNDEEP
python
Zoltán Fodor
Zoltán Fodor

Reputation: 123

How to declare many variables?

Here is the letters: 

letters='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'

I made a list of it with this:

chars=[]
for i in letters:
  chars.append(i)

So I have a chars list.

I need to all variables=0 each one to declare. And I wrote that:

for i in chars:
  chars[i]=0;

But there is an error message, like this:

Traceback (most recent call last):
  File "python", line 15, in <module>
TypeError: list indices must be integers or slices, not str

The question: How to declare these multiple variables?

Upvotes: 1

Views: 318

Answers (5)

Sohaib Farooqi
Sohaib Farooqi

Reputation: 5666

You can use either a list of tuples or a dict. A simple solution to do it:

>>> import string
>>> letters = string.ascii_uppercase + string.ascii_lowercase + string.digits
>>> chars = dict.fromkeys(letters , 0)
>>> chars
>>> {...'a': 0, 'b': 0 ....}

To use list of tuples:

>>> list(chars.items())
>>> [...('a',0), ('b', 0)...]

Upvotes: 2

Merlin
Merlin

Reputation: 25629

I think you mean this: 

letters='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'

# dict comprehension
dd = { x:0 for x in list(letters)}; dd
{'A': 0,
 'B': 0,
 'C': 0,
 'D': 0,
 'E': 0,
 'F': 0,
 'G': 0,
 'H': 0,
 'I': 0,
 'J': 0,
 'K': 0,
 'L': 0,
 'M': 0,
 'N': 0,
 'O': 0,
 'P': 0,
 'Q': 0,
 'R': 0,
 'S': 0,
 'T': 0,
 'U': 0,
 'V': 0,
 'W': 0,
 'X': 0,
 'Y': 0,
 'Z': 0,
 'a': 0,
 'b': 0,
 'c': 0,
 'd': 0,
 'e': 0,
 'f': 0,
 'g': 0,
 'h': 0,
 'i': 0,
 'j': 0,
 'k': 0,
 'l': 0,
 'm': 0,
 'n': 0,
 'o': 0,
 'p': 0,
 'q': 0,
 'r': 0,
 's': 0,
 't': 0,
 'u': 0,
 'v': 0,
 'w': 0,
 'x': 0,
 'y': 0,
 'z': 0,
 '0': 0,
 '1': 0,
 '2': 0,
 '3': 0,
 '4': 0,
 '5': 0,
 '6': 0,
 '7': 0,
 '8': 0,
 '9': 0}

update: 

dd['A'] = 13
dd
dd{'A': 13,
 'B': 0,
 'C': 0,
 'D': 0,
 'E': 0,
 'F': 0,
 'G': 0,
 'H': 0,
 'I': 0,

Or, 

list(letters) 
['A',
 'B',
 'C',
 'D',
 'E',
 'F',
 'G',
 'H',
 'I',
 'J',
 'K',
 'L',
 'M',
 'N',
 'O',
 'P',
 'Q',
 'R',
 'S',
 'T',
 'U',
 'V',
 'W',
 'X',
 'Y',
 'Z',
 'a',
 'b',
 'c',
 'd',
 'e',
 'f',
 'g',
 'h',
 'i',
 'j',
 'k',
 'l',
 'm',
 'n',
 'o',
 'p',
 'q',
 'r',
 's',
 't',
 'u',
 'v',
 'w',
 'x',
 'y',
 'z',
 '0',
 '1',
 '2',
 '3',
 '4',
 '5',
 '6',
 '7',
 '8',
 '9']

Upvotes: 0

aydow
aydow

Reputation: 3801

An alternative to list comprehensions is to use map

In [841]: letters='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'

In [842]: chars = list(map(lambda l: 0, letters))

Or if you want a dict like the other answers are suggesting

In [844]: dict(map(lambda l: (l, 0), letters))

I generally find list/dict comprehensions to both be faster and more readable (to me at least). This is just a different approach

Upvotes: 1

zvone
zvone

Reputation: 19332

The Solution

So, in short, what you want is a dictionary (mapping) of character -> 0 for each character in the input.

This is the way to do it:

letters='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'
chars = {char: 0 for char in letters}

The Problem

The problem with the original code was that there, chars was a list (because it was created as a list here: chars=[]), and characters were used as its indices.

So, the first time chars[i]=0; was executed (BTW, ; is not needed here), i was 'A' and chars['A']=0 produces the error.

Upvotes: 1

conr2d
conr2d

Reputation: 239

If you want to create 0-list with the length of string letters.

letters='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'
chars = [0 for _ in range(len(letters))]

Upvotes: 0

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