Python 3.x 在Python中将浮点转换为字符串时保留小数点

我正在为学校写一个自动取款机程序。我一直在做很多研究，试图弄明白为什么当我的数字像100.00时，当转换为字符串时，它们会变成100.0。我试过很多不同的方法，但总是出错

import sys

#account balance
acct_bal = float(500.25)
deposit_amount = float(0.00)
balance = float(0.00)
withdrawal_amount = float(0.00)

#<--------functions go here-------------------->
#printbalance function, choice B
def account_balance(acct_bal):
    print("Your current balance:")
    print(acct_bal)

#deposit function, choice D
def deposit(deposit_amount, balance):
    print("Deposit was $" + str(float(deposit_amount)) + ", current balance is $" + str(float(balance)))
    #print("Deposit was $" + "{:,.2f}".format(deposit_amount) + ", current balance is $" + "{:,.2f}".format(balance))
    #This one causes an error
    #Traceback (most recent call last):
    #File "G:/SNHU/1 - CURRENT/IT-140 Introduction to Scripting Python (10-30-17 to 12-24-17)/Module 5/ATM", line 29, in <module>
    #deposit(deposit_amount, balance)
    #File "G:/SNHU/1 - CURRENT/IT-140 Introduction to Scripting Python (10-30-17 to 12-24-17)/Module 5/ATM", line 17, in deposit
    #print("Deposit was $" + "{:,.2f}".format(deposit_amount) + ", current balance is $" + "{:,.2f}".format(balance))
    #ValueError: Unknown format code 'f' for object of type 'str'

#withdraw function, choice W
def withdrawal(withdrawal_amount, balance):
    print("Withdrawal amount was $" + str(float(withdrawal_amount)) + ", current balance is $" + str(float(balance)))

#User Input goes here, use if/else conditional statement to call function based on user input
userchoice = input("What would you like to do?\n")

if (userchoice == "D"):
    deposit_amount = input("How much would you like to deposit today?\n")
    balance = acct_bal + float(deposit_amount)
    deposit(deposit_amount, balance)
elif (userchoice == "B"):
    account_balance(acct_bal)
else:
    withdrawal_amount = input("How much would you like to withdraw?\n")
    balance = acct_bal - float(withdrawal_amount)
    withdrawal(withdrawal_amount, balance)

应该是>

Withdrawal amount was $100.00, current balance is $400.25

---

如果您使用的是Python3.x，那么有一种简单的方法可以完成这个过程，退出代码为0

value = 100.000

#the .2f specifys the number of trailing values after the decimal you want
final = "{:.2f}".format(value)

print(final)
#output:100.00
#NOTE: it will be in string
#if you want more formatting options you can check the python docs

---

可能重复使用带有

{：，.2f}.format（…）

的注释掉的行，并将数字而不是字符串传递给

存款

函数。（您需要将

输入的结果

转换为一个数字。）或者，

打印（“存款为$%.2f，当前余额为$%.2f”）%（存款金额，余额））

。最简单的方法是使用

str的
格式
功能。我得到以下错误：回溯（最近一次调用）：文件“G:/SNHU/1-当前/IT-140脚本Python简介（10-30-17至12-24-17）/模块5/ATM”，第44行，存款（存款金额，余额）文件“G:/SNHU/1-当前/IT-140脚本Python简介（10-30-17至12-24-17）/模块5/ATM”，第20行，存款金额=“{：，.2f}”。格式（存款金额）ValueError:类型为“str”的对象的未知格式代码“f”为什么在“{:'，'.2f}”处有逗号
value = 100.000

#the .2f specifys the number of trailing values after the decimal you want
final = "{:.2f}".format(value)

print(final)
#output:100.00
#NOTE: it will be in string
#if you want more formatting options you can check the python docs