如何解决未定义的名称错误？

Question

I am using hashing functions to calculate hash for various files. This is the code but I'm getting name error for "options" not defined. I don't think I'm doing it right.Any suggestions? I'm using options before in the code so whats the problem?

#!/usr/bin/python
import sys
import itertools
import hashlib

 # function  reads file and calculate the MD5 signature
 def calcMd5Hash(filename):
 hash = hashlib.md5()
  with open(filename) as f:
    for chunk in iter(lambda: f.read(4096), ""):
        hash.update(chunk)
    return hash.hexdigest()

# function  reads file and calculate the SHA1 signature
def calcSHA1Hash(filename):
hash = hashlib.sha1()
with open(filename) as f:
    for chunk in iter(lambda: f.read(4096), ""):
        hash.update(chunk)
    return hash.hexdigest()

# function  reads file and calculate the SHA256 signature
def calcSHA256Hash(filename):
hash = hashlib.sha256()
with open(filename) as f:
    for chunk in iter(lambda: f.read(4096), ""):
        hash.update(chunk)
return hash.hexdigest()

def main():
num = input("Select the hashing method you wish to use:\n 1. MD5\n 2. SHA1\n 

 3. SHA256\n")

options = {
    1: calcMd5Hash,
    2: calcSHA1Hash,
    3: calcSHA256Hash,
}

# test for enough command line arguments
if len(sys.argv) < 3:
    print("Usage python calculate_hash.py <filename>")
    return

hashString = options[num](sys.argv[1])

print("The MD5 hash of file named: "+str(sys.argv[1])+" is: "+options[num] 
(sys.argv[1]))

main()

Answer 1

Your input from the following line will be a string:

num = input("Select the hashing method you wish to use:\n 1. MD5\n 2. SHA1\n 3. SHA256\n")

you need to change your options to this:

options = {
    '1': calcMd5Hash,
    '2': calcSHA1Hash,
    '3': calcSHA256Hash,
}

Also, you could strip 'num' of any white space, just by doing:

num = num.strip()

This is how your main function should look like:

def main():
    num = input("Select the hashing method you wish to use:\n 1. MD5\n 2. SHA1\n 3. SHA256\n").strip()
    options = {
      '1': calcMd5Hash,
      '2': calcSHA1Hash,
      '3': calcSHA256Hash,
    }

    # test for enough command line arguments
    if len(sys.argv) < 3:
      print("Usage python calculate_hash.py <filename>")
      return

    hashString = options[num](sys.argv[1])
    print("The MD5 hash of file named: " + str(sys.argv[1]) + " is: "+ hashString)

if __name__ == "__main__":
    main()